sewhere to be found: but its chief value consists in its giving us the views of public events entertained by one of the principal actors; and in this way even its suppressions and perversions of facts are not without interest. It is written in a clear enough but in rather a poor and unimpressive style, the chief merit of which is its comparative freedom from the fashionable pedantry and quaintness of the age. Spotswood's biographer says that he had heard of no other works which he had left behind him; but Martine, in his notice of him in the 'Reliquiæ,' attributes to him - likewise a like tract, in good and refined Latin, called Refutatio Libelli de Regimine Ecclesiæ Scoticanæ, dedicated to King Charles I., a learned and eloquent piece, pitifully refuted by Mr. David Calderwood, under the name of Dido Clavius.' By his wife Rachel Lindsay, daughter to David Lindsay, bishop of Ross, of the house of Edzell, an honourable family in Scotland,' Archbishop Spotswood left two sons and a daughter. Of the eldest, Sir John Spotswood, his father's biographer, writing in 1655, says that he was then alive, though not in a plentiful, yet in a contented condition, not any way cast down or ashamed of his sufferings, but comforting himself rather, that, in this general ruin brought upon his country, he hath kept his conscience free, though his estate hath suffered.' These are like the expressions of a man speaking of himself, and would lead us to conjecture that Sir John Spotswood was the writer of this sketch of his father's life, and the editor of his 'History. The archbishop's second son, Sir Robert Spotswood, after having been made a lord of session by James VI., and lord president of that court by King Charles, was removed from the bench by the Covenanters in 1641, and in January, 1646, after the defeat of Montrose at Philiphaugh, was executed at St. Andrews, along with other adherents of that roalist general. A son of one of these brothers was also put to death at Edinburgh, in March, 1650, a few days after the execution of Montrose. The archbishop's daughter was married to Sir William Sinclair of Rosslyn. In the neighbourhood of his residence at St. Andrews, Archbishop Spotswood has left a memorial of his taste in the church of the parish of Dairsie, which,' his biographer tells us, he publicly at his own charges built, and adorned ... after the English form;' adding that if the boisterous hand of a mad reformation hath not disordered' it, it is at this time one of the beautifullest little pieces of churchwork that is left to that now unhappy country.' The church still stands, though disfigured in the interior, and stripped of whatever decoration it had that could be torn down without pulling the building to pieces. There is a view of it, and also of a house (now, we believe, entirely demolished) built by the archbishop in the neighbourhood of the church, in the last edition of Sir Robert Sibbald's History of Fife and Kinross,' 8vo., Cupar-Fife, 1803. Spotswood had purchased the estate of Dairsie. SPOUT, WATER, a meteorological phenomenon of the same class probably as the whirlwinds which raise pillars of sand in the deserts of Africa. The manner in which it has been observed to take place at sea is nearly as follows: Below a thick cloud the sea appears to be greatly disturbed within a circular area, whose diameter varies from 100 to 120 yards, the waves tending rapidly towards the centre of the agitated mass, where there is formed a vast body of water or aqueous vapour; from hence there rises, with a spiral movement, towards the cloud, a column of a conical form resembling a trumpet. Vertically above this ascending column there is formed in the cloud, but in an inverted position, a corresponding cone, whose lower extremity (the apex of the cone) gradually approaches the summit of the ascending column; and at length both are united, the diameter at the place of junction being only two or three feet. The water-spout is said to be accompanied, during its formation, by a rumbling noise, and, when complete, it assumes a magnificent appearance. The whole column, which extends from the sea to the clouds, is of a light colour near its axis, but dark along the sides, which gives it the appearance of being hollow. The spout appears to move with the wind, though, even when no wind is felt, it sometimes varies its position, tending successively in different directions. It frequently happens that the upper and lower parts of a column move with different velocities, and then, after the whole has taken an inclined position, the parts separate from one another, often h a loud report. Previously to the rupture of the column, the dark parts seem to be drawn upwards irregularly, leaving only a slender tube in connection with the water below. The whole of the vapour is at length absorbed in the air, or it descends into the sea in a heavy shower of rain. The duration of the phenomenon is various: some spouts disappear almost as soon as they are formed, and others have been known to continue nearly an hour: occasionally they form themselves, continue for a short time, vanish, and again appear, and so on several times successively. No ship could escape if it were carried within the vortex; and mariners formerly endeavoured to accelerate the fall of the column by a discharge of artillery towards it. (See a description in Falconer's Shipwreck,' canto 2.) Water-spouts are occasionally seen above land, and conse quently there is then no ascending column of water or vapour to meet that which descends from the clouds. In Dr. (Sir David) Brewster's Journal of Science' (No. 5' there is an account of one which was seen in France: it is stated to have appeared like a conical mass of vapour, and to have given out a strong sulphureous smell; flashes of lightning issued from it, and it threw off a great quantity of water. It moved forward in one direction over high grounds and valleys, and it crossed the course of a river, but on coming to hills of a conical form, it passed round them. Water-spouts have occasionally been witnessed in this country. In 1718 one of them burst in Lancashire, when, at the place where it fell, the ground was torn up to the extent of about half a mile in length, and to the depth of seven feet, so as to lay bare the surface of the rock underneath. (Phil. Tr., No. 363.) The formation of water-spouts has been ascribed to a whirling motion produced in the air by currents coming in opposite directions; it has been supposed that the particles of vapour in the upper regions thus acquire, by the centrifugal force, a tendency to move towards the exterior parts of the column, leaving the interior void or in a rarefied state. Te pressure of the atmosphere being thus removed from the surface of the sea or ground immediately below, that whah takes effect on the surrounding water (when the spout s formed at sea) must impel the latter towards that part, and cause it to rise into the space where the partial vacuum exists. There is great probability that the elevation of the sea under the cloud is in part caused by the rarefaction of the air; but as the pressure of the atmosphere could only raise the water in a perfect vacuum to the height of about 30 feet, and as the height of a water-spout is known to be sometimes about half a mile, some other explanation of the phenomenon must be sought for. From the occurrence of such phenomena at seasons when the electrical principle in the air is most active; from the sulphureous smell, the flashes of lightning, and the storms of rain or hail by which they have been accompanied, and from the destruction of trees, buildings, &c. which they have produced, their formation has been ascribed with great pro bability to the action of electricity. The cloud and the sa or ground may be in opposite electrical states, and therefore there will be a mutual attraction between them; this will of course be attended by all the consequences of a vast dis charge of the fluid; but it must be admitted that the precise manner in which the phenomena are produced by the agency of electricity is not yet satisfactorily known. SPRAGGE, SIR EDWARD, was a distinguished commander in the naval battles between the English and Dutch during the reign of Charles II. Of his parentage, the date of his birth, and the circumstances of his early life, there are no records. He fought as a captain in the battle between the English and Dutch, June 3, 1665, and for his gallantry on that occasion received the honour of knighthood. He was engaged in the four days' battle which took place in June, 1666; and also in the following one of July 24th. When Van Tromp sailed up the Thames in 1667, he defended Sheerness; which however, from the weak state of the garrison, he was compelled to abandon. He afterwards collected a few frigates and fire-ships, and when the Dutch admiral Van Nes sailed up the Thames Spragge engaged him, burnt some of his ships, and chased him out of the river. In 1671 Sir Edward Spragge fought against the Algerines, burnt several of their vessels, and did considerable damage to the castles and towns on the coast of Algiers. In the battle of Solebay, May 28, 1672, he sunk a Dutch ship of 60 guns. In 1673 he was made admiral of the blue, and on the 28th of May in that year another fight took place, in which Spragge and Van Tromp were compelled to change their ships two or three times in consequence of the damage done to them. On the 4th of June he fought Van Tromp again, and the two admirals were once more compelled to leave their shattered vessels. On the 11th of August another similar contest took place between them, when Spragge, passing in a boat from the battered St. George to the Royal Charles, was drowned, a shot having struck and sunk the boat. He was buried in Westminster Abbey. Sir Edward Spragge has been highly praised by his contemporaries, not only for his courage and skill as a commander, but for his gentlemanly manners and amiable disposition. (Campbell's Lives of the Admirals.) SPRAIN, or STRAIN, is an injury of muscular or tendinous tissues, resulting from their being forcibly stretched beyond their natural length. Its ordinary consequence is, after the first pain is gone by, to produce some degree of swelling, and a considerable dull aching pain of the injured part, which is greatly increased by any movement of it. These signs are due to an inflammation of the sprained tissues, which partakes of the slowness and obstinacy that characterise all the diseases of the tendons and ligaments, and which, if not early and duly attended to, frequently terminates in thickening, rigidity, and even more serious disorganization of them and the adjacent parts. Athens Oxon.,' among which is a Life of Cowley, and some sermons and letters: there is also a letter of his among the Lansdowne MSS., British Museum. His prose style is remarkable for choiceness of expression and beauty of structure: he is styled by Wood a commanding and eloquent preacher, and this praise is confirmed by Burnet. Ho wrote a few short poems, in the manner and with all the faults of the school of Cowley. The longest of them, 'The Plague of Athens,' is, to borrow Sprat's own words in the dedication of it, an example how much a noble subject is changed and disfigured by an ill hand.' (See Some Account of the Life and Writings of the Right Reverend Father in God Thomas Sprat, DD.,-with a True Copy of his Last Will and Testament,' London, printed for E. Curll, 1715; and Johnson's 'Lives of the Poets.') SPRENGEL, CURT, one of the most learned physicians and botanists of the last and present century, was born on the 3rd of August, 1766, at Bolderkow in Pomerania, where his father was a clergyman. His early studies were entirely directed by his father, and he is represented at the age of fourteen as being conversant not only with the Latin and Greek classics, and some modern languages, but to have made considerable progress in Hebrew and Arabic. Nor was his attention confined to languages, for at this age he published a little work on botany, in a series of letters, entitled Halle, and devoted himself to both theology and medicine, but he soon gave up the former for the latter. In 1787 he took his degree in medicine, and on this occasion presented as his thesis a paper entitled Rudimenta Nosologiæ Dynamicæ. During his medical studies he kept up his acquaintance with the antient languages, and extended his knowledge of those of the East, and was thus remarkably qualified for the study of the history of medicine. To this department he applied himself, and in 1789 was appointed extraordinary professor of medicine in the university of Halle. In 1795 he was made ordinary professor of the same department. Although his application to the study of medicine was great, and he had already commenced his work on the History of Medicine,' and had published his Manual of Pathology,' he yet found time to cultivate his acquaintance with plants, and in 1797 was appointed professor of botany. To this department he applied the same learning that he had done to medicine, and his prolific pen has furnished the most complete history of botany extant. The treatment to be adopted for sprains is the imme-Botany or Ladies.' In 1784 he commenced his studies at diate application of leeches, in number proportionate to the severity of the injury and the importance of the part. They should be repeated till the pain and swelling are distinctly decreased: the part should be kept perfectly at rest and cool, and the patient's general health should be kept or made good. When the pain has nearly ceased, and there remains little more than stiffness of the injured part, stimulating liniments (the common soap liniment, or a mixture of hartshorn and oil, for example) may be used. SPRAT. [CLUPEIDE.] SPRAT, THOMAS, was born in 1636, at Fallaton in Devonshire. He was the son of a clergyman, and was educated at Wadham College, Oxford, of which foundation he became fellow. He took the degree of MA. in 1657. In 1659 he published a poem on the Death of Oliver Cromwell, and another, 'The Plague of Athens.' Having been ordained after the Restoration, he was made chaplain, first to the duke of Buckingham, whom he is said to have assisted in writing The Rehearsal,' and afterwards to the king. At this time he was made one of the original fellows of the Royal Society, and in 1667 published its history. In 1668 he was made prebendary of Westminster, in 1683 dean of Westminster, and in 1684 bishop of Rochester. In return for these marks of royal favour, Sprat in 1685 published a history of the Rye-house plot, entitled 'A true Account and Declaration of the horrid Conspiracy against the late King, his present Majesty, and the present Government;' but he repented of having written this work; and when requested by James, after Monmouth's execution, to add a second part, he refused, on the ground that the lives of many innocent persons would be endangered thereby. (See his letter to the earl of Dorset, written in 1689, printed in 1711, 4to.) In the following year he was appointed one of the commissioners for ecclesiastical affairs: he voted in this office for the acquittal of the bishop of London; and in 1688, though he had himself acknowledged the king's declaration of Toleration, he refused to take part in any proceedings against the disobedient clergy, and withdrew from the commission. On the abdication of James, Sprat was one of those who in the convention held on that occasion proposed the appointment of a regent; but after the settlement of this question, he did not refuse allegiance to William. In 1692 an attempt was made to implicate the bishop in a pretended plot for restoring James, his signature having been fraudulently obtained by two men of infamous character, Robert Young and Stephen Blackhead. He succeeded after some little time in triumphantly establishing his innocence and the villany of his accusers. From this time till his death, May 30, 1713, at Bromley in Kent, he lived undisturbed by any political troubles. His property was bequeathed to his son Thomas Sprat, archdeacon of Rochester. Burnet, who appears to have viewed Sprat with the jealous eye of a rival, speaks slightingly of his moral character, but his conduct on many occasions shows an integrity superior to the feelings of personal gratitude towards the king. There is a list of his works in Wood's Through his works he became celebrated throughout his native country, and was called upon to fill very important chairs. In 1803 he was invited to Marburg to fill the chair vacated by Baldinger; in 1809 to Dorpat; and on the death of Willdenow, in 1812, he was invited to occupy his place at Berlin. All of these he refused, and remained his whole life at Halle. The fame of his learning however was not confined to Germany; almost every country in Europe sought to confer honours upon him. Upwards of seventy learned societies and academies sent him their honorary diplomas, and many kings conferred upon him their orders of distinction. These however were objects at which he never aimed, and which he never allowed to divert him from his favourite studies. He was one of the most industrious and learned men of his age, but whilst his great learning enabled him to become perfectly conversant with what had been done by previous writers, he did not neglect to observe for himself, and add the fruit of his own experience to that which had been previously produced. The early part of Sprengel's life seems to have been more particularly directed to medicine. In 1788 he published a defence of Galen's doctrine of fever, and in 1798 an apology for Hippocrates. In 1792 the first part of his History of Medicine' appeared, and was not completed till 1820. These works were followed by smaller ones on various departments of the science of medicine, a complete view of which was given in his 'Institutiones Medicæ,' a work in six volumes, which appeared at various intervals from 1809 to 1816. In this work the whole field of medical science is gone over, and each department displays the author's characteristic learning. As a botanist Sprengel stands very high. He had in early life contracted a love for botany, and after his appointment to the professorship of that science in Halle, he never ceased, till disabled by disease, contributing important additions to its literature. In 1798 he published his Antiquitates Botanica,' which was followed in 1808 by his Historia Rei Herbaria.' In these works he has brought his knowledge of antient languages to bear upon the illustration of botany in the earliest times, and in the latter work the history of the science is brought down to the period at which it was written. To descriptive botany he made great additions, especially in the Flora Halensis,' published in 1806, and subsequent editions. These works were illustrated by many plates from his own pencil. Besides these he has published many other papers in this department of botany. He took a part with Schultes in preparing an edition of the Systema Vegetabilium' of Linnæus, and subsequently, in 1824, published an edition of that work himself, with an appendix. He also described a part of the Brazilian plants, collected by Sellow, in his Neue Entdeckungen im ganzen Umfang der Pflanzenkunde,' published in 1820. In the systematic arrangement of plants he established many improvements, both in the Linnean and natural systems, the principal of which are contained in his works on descriptive botany. In 1811 he published a work on physiological and descriptive botany, entitled, Von dem Bau und der Natur der Gewächse,' in which he has given the result of the labours of others, and added many new observations of his own. In 1822 he published a German translation of Theophrastus's Natural History of Plants,' and in 1829 a new edition of 'Pediani Dioscoridis Anazarbei de Materia Medica Libri v. His last work was an edition of the Genera Plantarum' of Linnæus, in 1830. His eldest son William was professor of surgery at Greifwald, and died in 1828. This loss affected the father very severely, and he never recovered the stroke. He was at tacked by several apoplectic fits, and died in one of these seizures, on the 15th of March, 1833. SPRING. [SUMMER and SPRING.] SPRING, in Mechanics, is an elastic plate or rod, which is employed as a moving-power, or a regulator of the motions of wheel-work; also to ascertain the weights of bodies, or to diminish the effects of concussion. The elder Bernoulli was the first whose attention was directed to the curvature assumed by elastic bodies, and he succeeded in resolving the problem in the case of a rectilinear plate being fixed at one end and bent by a weight applied at the other: it being assumed as a principle that, at any point in an elastic body, the force by which the body when bent by any power endeavours to recover its previous position is proportional to the angle of contact at that point; that is, to the angle which a tangent to the curve surface of the body makes, at the point, with that surface. In order to give some idea of the manner in which the effects of elasticity are to be determined mathematically, let AB be a thin elastic plate immoveably fixed at A, and bent into the form AB' by a power P applied at B, and let a, a, aa' be two consecutive elementary portions of the bent plate: let also E represent the unknown force of elasticity acting perpendicularly to aa' by which that element tends to recover the direction a, a, from which it has been made to deviate by the power at B; and for simplicity let it be supposed that this power acts in the direction B'C parallel to AB. Let fall ap perpendicularly on B'C; also represent B'p by x and ap by y. Then, by mechanics P. y expresses the momentum of the power at B' to bend the plate at a, and in the case of equilibrium we have P. y E. But E varies with the angle of contact, or the angle between the element aa' and a, a produced, and that angle in any part of AB' varies inversely with the radius of curvature at that part; therefore let r be the known radius of curvature at a point where the force of elasticity is given, and let this force be represented by e: also let R be the radius of curvature at a point, as a, where the force is represented by E. Then :e:: : E, or = E, and putting E' for er, we R R E' g 1 er have P.y= tial expression for the radius of curvature, the elastic force might be obtained by the processes of integration. The integral however can only be obtained approximately. Substituting in place of R the differen where C is the tangent of the angle of contact at B'. If, on account of the smallness of this angle, C be neglected, it will follow, when x is made equal to B'C, that the whole deflection AC or BB' will vary nearly with the weight P, and with the cube of the length of the spring. The use of a spring as a moving-power may be best exemplified in its application to watch-work. The mainspring of a watch is a thin and narrow plate of well-tempered steel, which is coiled in a spiral form: one of its extremities is attached to a pivot or axle, and the other to the interior circumference of the cylindrical box in which it is contained. In being wound, the spring closes round the axle, and afterwards, in the effort by its elasticity to recover its former position, it turns the cylinder in a contrary direction: thus the chain which is attached to the exterior circumference of the cylinder and to the fusee causes the latter to revolve. A slender and highly elastic spring of a like form is employed to produce a vibratory motion in the balance ring of a watch: one extremity of the spring is attached to the axle of the balance, and the other to some part of its circumference. If a movement of small extent about the axle be given in one direction to the balance, the spring will be compressed near the axle, and, in the effort to recover its previous state, the balance-ring will be moved round in a contrary direction; but the force of elasticity carries any point in the ring beyond the place which it occupies when the ring is in a state of rest; and when that force is destroyed by the compression again produced in the spring, near the axle, the balance is made to return in the direction in which it was at first moved. Thus an alternate motion in the balance-ring is continued; the time of the vibrations, and consequently the velocities with which the wheels revolve. depending upon the force of elasticity in the spring. The elastic power of the spring varies with the tension, and is directly proportional to the angle through which the spring is wound about the axle; and thus the vibrations of a spring, like those of a pendulum in a cycloidal arc, are isochronous. [ELASTICITY, p. 327.] The length of the spring and the diameter of the balance are increased by heat and diminished by cold; consequently, without some compensating power, the times of vibration will vary according to the changes of temperature. When a carriage moving along a level road passes suddenly over an obstacle, so that a point in the circumference of the wheel is in contact with the obstacle, the centre of the wheel describes a circular arc about the point of contact as a centre; and then, if the carriage is perfectly rigid, a portion of its velocity will be lost. In order to maintain that velocity, an additional force of draught would be necessary; and an expression for this additional force is investigated in Whewell's Mechanics' (art. 261, and the following). Part of this additional force is employed in counteracting the motion of ascent, and the remainder, which is generally much the greater quantity, in diminishing the effect of the sudden change which takes place in the direction of the motion of the carriage. This latter part may be in a considerable degree removed by the use of springs; for then, on the wheel meeting the obstacle, the suspended body of the carriage bending the springs by its weight, the centre of gravity of that body is made to describe a curve line, to which its previous rectilinear direction is a tangent; and thus the jerks which arise from movements in directions making finite angles with one another are avoided. The force of draught required in addition to that which is due to friction, when a stiff carriage passes over a roughly paved road, varies as the square of the velocity and the height of the stones directly, and as the radius of the wheel SPRING-BALANCE, a machine in which the elasticity of a spring of tempered steel is employed as a means of measuring weight or force. The name is most commonly applied to machines for the former purpose; those employed to ascertain the muscular strength of men and animals, the amount of power required to move a carriage or a boat, or any other force applied in the form of a pull, being called dynamometers. | a spring-dynamometer for this purpose, especially when the carriage is moved by animal power, some inconvenience is occasioned be the vibration of the index with every trifling variation in the force applied, to remedy which Mr. H. R. Palmer contrived an apparatus in which the quick vibration of the spring is checked by means of a piston moving in a cylinder filled with oil. A very narrow space is allowed for the oil to pass between the edge of the piston and the cylinder, so that a considerable resistance is opposed to the motion of the piston and the springs, and the index consequently represents the mean amount of force applied without being affected by sudden variations. The ingenious method adopted by Mr. Martin for transmitting the motion of a spring to an index moving upon a circular dial-plate, is applicable to spring-balances of other than the helical construction. It was used by M. Hanin, a French gentleman, who was rewarded by the Society of Arts, in 1790, for an apparatus for showing at one view the weight of an object according to several different scales or systems of weights. His machine, which is described and figured in the ninth volume of the Society's Transactions,' One of the simplest kinds of spring-balance is that which, consists of a dial-plate, on which are marked several concenwhen employed as a weighing-machine, is known as the tric circles, divided according to the systems of weights spring or pocket steelyard. It consists of a helical spring used in different countries, and an index moved by a rack formed by bending a steel wire spirally round a cylindrical and pinion, as before described. The spring, instead of mandril or axis, so as to form an extensive series of convo- being of a helical form, is semicircular; its upper extremity lutions. This spring is placed in the interior of a tube of being firmly attached to the back of the dial-plate by means brass or iron, closed at both ends; one end of the spring of screws, while its lower end is attached to the hook which abutting against the plate which closes the lower end of the carries the weight, and the sliding rack by which the index tube. A rod, having a hook or loop at its lower extremity, is moved. Marriott's patent weighing-machine is very to hold the article to be weighed, passes through a hole in similar to that of M. Hanin, but the spring is a perfect elthe bottom of the tube, and up the inside of the spring. At lipsis, with its longer axis laid horizontally. The stem to the upper end of this rod is a small plate, which slides up which the ring for holding the apparatus is attached is and down like a piston in the tube, and rests upon the fastened by a nut and screw to the middle of the upper side upper or free end of the spring; thereby causing it to col- of the spring; and the rack, with the hook which holds the lapse when a heavy body is attached to the hook at the bot-article to be weighed, to the corresponding point on the tom of the sliding rod. The machine is supported by means lower side of the spring. The spring, rack, and pinion are of a hook or ring attached to the upper end of the tube; enclosed in a circular box at the back of the dial-plate, the and the extent of the motion of the spring, and conse- periphery of which serves as a stop to prevent the spring quently the weight of the body suspended from it, are indi- from being overstrained. A similar apparatus, contrived cated by the degree to which the rod is drawn out of the by M. Regnier, has been used as a dynamometer, as well as tube. For this purpose a graduated scale is engraved upon a weighing-machine. the rod; the divisions indicating the extent of compression produced in the spring by the application of known weights. Several spring-balances on the same principle are made for various purposes. That known as Salter's balance has a brass plate attached to the tube or cylinder, within which the spring is enclosed, and a vertical slit through the plate and tube. A scale is engraved on the face of the brass plate, and the weight is indicated by a pointer which moves up and down with the spring, with which it is connected through the vertical slit in the tube. A very delicate balance of this kind has been manufactured for weighing letters, since the introduction of Rowland Hill's plan of penny postage. In 1814 the Society of Arts rewarded Mr. Martin for an index weighing-machine,' acting upon the same principle, but having a circular dial-plate and a revolving pointer or index, resembling the hand of a clock. On the axis of the index, but at the back of the dial-plate, is a toothed pinion, which is turned by a straight rack attached to the vertical rod, which rises and falls with the spring. The index remains in a vertical position when the balance is unloaded, and deviates more or less from it when a weight is attached to the hook. One advantage of this construction is that the point of the index traverses a much greater space than the spring itself, so that a very small movement of the spring becomes readily discernible. Spring-balances with helical springs are applied to several useful purposes besides that of ascertaining the weight of bodies. A spring of this character is sometimes used to hold down the lever of the safety-valve in a steam-engine boiler, the movement of the index also showing the pressure of the steam. Such an apparatus is especially useful in a locomotive engine, the shaking motion of which might derange a valve loaded with moveable weights. A helical spring-balance forms also a good cable-stopper. When applied to the measurement of muscular force, the tractive power of a locomotive carriage, &c., one end of the cylinder in which the spring is enclosed is made fast to an immoveable object, and the power to be measured is applied to the sliding-rod. If used to ascertain the force necessary to draw a carriage, the spring is placed between the carriage to be drawn and the power employed to draw it. In using P. C., No. 1407. A scale-plate or dish may be added when necessary to any of the spring weighing-machines which have been described. On account of the absence of weights, and the great simplicity of their application, spring-balances are very useful in cases where extreme accuracy is not required, especially when a portable weighing-machine is desirable. Machines for ascertaining the weight of the human body are often made on this principle, a kind of chair being suspended from the spring. It has been proposed to apply the elasticity of steel springs for indicating the weight of very heavy bodies, such as loaded carriages; but we are not aware that the suggestion has been carried into effect. The apparatus commonly used for this purpose is described under WEIghing-Machine. (Manufactures in Metal, vol. ii., p. 297, in Lardner's 'Cabinet Cyclopædia; Hebert's Engineer's and Mechanic's Encyclopædia, arts. Dynamometer' and Steelyard.") SPRING-CARRIAGE. The progress of a wheel-carriage, even upon the best of roads, is continually impeded by the wheels coming in contact with, and being compelled to rise over, undulations or asperities of surface, which check their rolling motion. In a well-constructed iron railway this kind of resistance is reduced to the minimum, but it is not entirely obviated, as no degree of care which can be bestowed in practice will prevent small irregularities at the joints, or minute undulations in the surface of the rails. On a stone pavement, owing to the greater frequency of the joints, and the comparative roughness of the stone, deviations from a perfectly smooth surface are more frequent and greater in amount. Indeed in many old rough pavements, owing to the openness of the joints, and the wear of the upper edges of the stones, the road consists of a series of blunt ridges, in passing over which the motion of the wheel can be no other than a succession of jolts. The surface of a well-made road of broken stone, when in perfect order, presents few important asperities; but when metal or broken stone has been recently laid on, it is exceedingly rough. If a rigid carriage be drawn over any of these surfaces, the irregularities which affect the path of the wheels will be communicated through them to the body, to which they will impart a jolting or vibratory motion VOL. XXII.-3 D As an When the carriage is moved very slowly, the pata traced | hide, the quick vibration when on a rough road is stated by the axle, or by any point of the body, supposing the to be almost as unpleasant as actual concussion. vehicle to have but two wheels, and to be free from other illustration of the necessity of weight to render a suspende disturbing causes, will be nearly the same as the surface of carriage agreeable, Adams observes, Those who have trathe road in the track followed by the wheel; every undula- velled in the heavy and heavy-loaded French diligences at tion of the surface being transmitted to the body of the car- a slow rate will not have found their motion unpleasant, riage. In a four-wheeled carriage the movement of the but whoever has experienced the movement of the rude body will be influenced by the discordant motions of the leather-covered carts formerly used for the conveyance of fore and hind wheels; and also, supposing its construction the French mail will never wish to repeat the experiment.' to be perfectly rigid, it will be continually liable, owing to To remedy the defects of the primitive slung carriage, it was the imperfections of the road, to have the whole of its desirable to render the pillars from which the straps were weight thrown upon three wheels, whereby the frame- suspended somewhat elastic. This could not be read. y work will be exposed to injurious strains. With either kind effected with wood, because the pillars were necessary of carriage, if the speed be increased, the impulses received short, and therefore stiff. Hence arose the use of elasti from the irregularities of the road will follow each other in steel supports, which have gradually assumed the form such rapid succession as to set the carriage in violent vibra- now well known as C-springs. These were formerly usei tory motion, throwing the weight alternately from side to for almost all kinds of spring-carriages; but the great tu side, and causing the wheels to leap from one prominence provement of our roads has made way for the introduction, to another; and so producing a series of concussions tending in all stage-coaches, and in many private carriages, of the to the rapid destruction of the vehicle, and extremely un- less yielding, but lighter and more compact, straight and pleasant to the riders. To enable it to sustain such strains, elliptic springs. the framework of carriages which are unprovided with Straight springs of steel probably owe their origin to t springs or contrivances for eluding concussion must be straight wooden springs occasionally used in light vehicles made very strong and heavy ; and the destructive and pain- in this and other countries. Used either singly or in comful effect of increasing the velocity of inelastic carriages bination, they afford sufficient elasticity for many purposes. would alone have been sufficient to limit the speed of vehi- without raising the body to an inconvenient degree, or cles intended for the conveyance of passengers before the terfering with its form; since they may be placed entirely introduction of springs. Alluding to the earliest English beneath it, and require but little room for their play. Elip stage-coaches, which had no springs, Edgeworth observes, tical springs have, in some degree, the same advantages 'The danger of sitting on the roof of the coach was then but they require rather more depth than straight spring never hazarded by outside passengers; they were stuffed in Carriage-springs are usually formed of several tinn straw in a huge clumsy basket, that was fastened precisely plates of steel, of various lengths, so laid and fastened toge over the hind axletree of the coach.' 'When springs came ther that the spring shall be thick in the centre, or at ib: into fashion for gentlemen's carriages,' he continues, 'stage- end by which it is fixed, and thin, or consisting of only a coaches were obliged to adopt them; and by degrees out- single plate, at the end or ends where the greatest play side passengers ventured to sit on the tops of coaches, and is required. The steel used is of coarse quality, and has coachmen found, to their surprise and profit, that their little carbon in its composition. It is fashioned by rollinghorses could draw a greater number of passengers than machinery to the transverse dimensions required, which formerly.' vary from one inch and a half to three inches in width, by one-eighth of an inch to three-eighths of an inch or halfan inch in thickness. The plate forming the back of the spring is usually thicker than the rest, on account of its being tor longest, and having its ends formed into bolt-eyes, to receive the bolts by which the body is connected with it. With this exception, it is not usual to make any difference in thickness in the several plates of a spring, notwithstand ing their different lengths. The mode of construction may be understood from the following description, extracte. from Adams, of the process of making a straight doub spring; that is, a spring which is fixed in the centre, ar! acts or plays towards each extremity. The spring described is intended to rest upon the axle, which it crosses at right angles: One of the simplest means of alleviating concussion to the riders is that often adopted in light carts, of suspending the seat from the sides of the body by leather straps or lashings. Next to this is the use of straps to suspend the body itself, an expedient which seems to have been occasionally resorted to from a very early period. The first approach to a slung carriage which had been met with by Mr. Adams, occurs in an illustration to a Saxon MS. in the Cottonian Library, of which an account is given in his interesting work on English Pleasure-Carriages.' It is found in a representation of the meeting of Jacob and Joseph; the latter is seated in a kind of chariot, consisting of a hammock suspended from a framework of wood, mounted upon four wheels. The vehicle in which Jacob is seated is described as a cart, which, from its primitive simplicity, may be supposed to be a faithful representation of those in common use at the time when the illumination was executed. It is supposed from this illustration that carts were then used by the common people, and the superior kind of vehicle by the principals only. With very few exceptions, it appears that slung or suspended carriages were not used until the seventeenth century. In the early carriages of this kind the straps were usually attached to a framework of wood at each end of the vehicle, rising to a considerable height above the axles. The antique fourwheeled carriages of Europe used for state purposes are mostly constructed on this plan, and their great weight and slow movement prevent any violent concussion.'' Many of the public stage-coaches of France,' proceeds Mr. Adams, are suspended on the same principle, as well as those of the United States and Canada: for in the latter countries, though there is not any lack of enterprise or want of energy to improve the public vehicles, it is found by experience that the imperfect condition of the roads precludes the possibility of using steel springs with a due regard to economy. A serious disadvantage of this construction is the great length of carriage that it renders necessary, and the cumbrous character of the wooden framework which supports the braces. The carriage must also be heavily loaded, in order to make the motion tolerably comfortable, especially when the straps or braces are suspended from points not much higher than the bottom of the body. In the light carri-coche of Buenos Ayres, which is supported on two nearly straight braces, or twisted cords of untanned The back plate being cut to the proper length, the ends are slightly tapered in the direction of their thickness, b the hammer, and curled round a mandril of the size of the suspension-bolt. The side which fits against the other plates is then technically middled;' i. e. it is hollowed ty hammering, so that the centre may be sunk below the edges. The next plate is then cut nearly as long as the first, and the ends are tapered down; after which it middled' on both sides. A slit is then cut at each end, about an inch in length and one-quarter of an inch wide, m which a rivet-head is to slide and connect it with the first plate; so that whichever way the force or weight may act these two plates sustain each other. At a little distanc from this rivet, a stud is formed upon the under surface by a punch, which forces out a protuberance, sliding in a in the next plate; by which contrivance all the plates are retained parallel while they work. The next plate is pre pared in precisely the same manner, with the exception that it is from three to four inches shorter at either end; and so on with as many plates as the spring may happen to consis of. The last one, like the first, is only middled on one side.' After the plates are thus wrought into the form required, they are hardened by heating them in a hollow fire. and then plunging them into water. They are subsequent tempered by drawing them again through the fire, until they become so hot that a stick rubbed over the surface wil be kindled to a blaze. Any accidental warping acquired a these processes is removed by a hammer, the plates being slightly warm during the operation, to avoid the nak of breakage. This is called setting, and is, at best, an opera |