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come within the sphere of our cognisance. These properties diagram this correspondence occurs at the eighth division or are distinguished into general and special. The former are the vernier, counting from the point n. This coincidence those which belong to all bodies, of whatever kind and in what shows that the fraction to be measured is equal to eight-tenths. ever state they may be examined. The properties necessary to | In other words, the divisions on the vernier being smalier than be considered at this time, areimpenetrability, extension, divisi- / than those on the fixed rule by one-tenth, it follows that if we bility, porosity, compressibility, elasticity, mobility and inertia. begin to count at the point of coincidence, and proceed in the Special properties are such as are observed in certain bodies, direction from right to left, each guccessive degree on the ver. or under certain physical conditions. Of this kind are solidity, nier falls in arrear of the corresponding degree on the fixed fluidity, tenacity, ductility, malleability, hardness, transparency, rule by one-tenth. Hence it follows, that in the case under colour, &c. For the present we shall only be concerned with consideration from the extremity n of the vernier, to the fourth the general properties of matter already mentioned; but it is division on the fixed rule, the intervening space is eight-tenths, proper to remark that impenetrability and extension, are not and we arrive at the final conclusion that the length of the so much to be regarded in the light of general properties of object m n to be measured, is equal to four of the divisions of A B matter as the essential attributes of matter itself, and which plus eight-tenths. Consequently if the divisions on the great or serve to define it. Furthermore we may here remark, that fixed rule are hundredths of inches the length of m n will be the terms divisibility, porosity, compressibility, and elasticity obtained almost exactly correct to one-thousandth of an inch, only apply to bodies regarded as made up of aggregated mole- Were it desired to be still more accurate, to obtain the length cules; they are inapplicable to atoms.

correct to the two or three thousandth part of an inch, it would Impenetrability.-

This is the property by virtue of which no then be necessary to divide a B into hundredths of an inch, to cut two material elements can simultaneously occupy the same off the vernier rule until its length should be equal to nineteen point in space. This property, strictly speaking, only applies or twenty-nine divisions of the great rule, as the case might be, to atoms. In a great number of cases, bodies appear to be and finally to divide the vernier into twenty or thirty equal parts. susceptible of penetration. For example, there exist certain But when such minute divisions as these have to be observed, alloys, of which the volume is less than the joint volume of the and the exact line of coincidence between the degrees of the vermetals entering into their composition. *Again, on mixing nier and the fixed rule accurately read off, the aid of a lens is water with oil of vitriol or with alcohol, the mixture contracts absolutely necessary. The vernier is not invariably a linear in volume. Such phenomena do not represent actual penetra- measure, as we have already described it; very frequently gra. tion. The appearance is solely referable to the fact, that the duated circular arcs are supplied with verniers, which are materials of which the acting bodies are composed are not in then usually engraved in such a manner that fractions of a actual contact. Certain intervals exist between them, and degree are read off in minutes and seconds. It may be proper these intervals are susceptible of being occupied by other here to remark that the vernier is also occasionally termed a matters, as will be demonstrated further on, when we come to nonius, and still more frequently in mathematical books of a treat of porosity.

past era, the nonius vernier. It derives this name from Nunca, Extension.—This is the property which every material body a Portuguese mathematician, who is considered by some to possesses of occupying a limited and definite portion of have been its inventor. This, however, is not the case. The space. A multiplicity of instruments has been constructed, instrument of Nunez, although designed for accomplishing a having for their object the measuring of space. Amongst similar purpose with the vernier, differed from it in some in. these the vernier and the micrometric screw

are very

portant respects, and was far less efficient. important; we will therefore proceed to their consideration. The Micrometric Screw and Dividing Machines. The term microThe Vernier is so called from the name of its inventor, a metric is applied to that variety of screw employed for measur. French mathematician, who died in 1637. This instrumenting with precision the extension of length and breadth. It enters into the construction of numerous kinds of apparatus follows, from the very nature of a screw, that when it is well used in the study of the physical sciences, such, for example, as and accurately made, its pitch, or the interval existing between barometers, cathetometers, goniometers, &c. It is composed of any two successive threads, must be everywhere throughout its two engraved rules, the larger of which a B (fig. 1), is fixed and length the same. From this it follows, that if a screw be rota. divided into equal parts. The smaller rule is moveable, and to ted in a fixed nut, the former will advance a certain equal disthis in strict language the term vernier is alone applicable. Itance for each revolution, the rate of advance being proporTo graduate the vernier, the process is as follows. First of tionate to the degree of obliquity of the screw-thread. It fol. all it is cut to such a length as corresponds with nine divisions lows, moreover, that for every fraction of a turn, say doth, it of the large or fixed rule. It is then divided into ten equal only advances the both of the length of an interval between parts, from which arrangement it follows that every division any two threads. Consequently if this interval be equal to a of the rule a d is smaller than a division of the rule a B by hundreth of an inch, and if at the handle extremity of the screw one-tenth.

there is attached a wheel or circle graduated into 400 divisions,

and turning with the screw, then on turning the graduated Fig. 1.

wheel through only one division, the screw itself will be caused В

to advance to the extent of one 400th of an inch,

Dividing machines, as they are termed, depend on the application of this principle. Fig. 2 represents a dividing machine, intended for the division of straight lines. It is composed of a long screw, the thread of which ought to be perfectly regular, working through a fixed metallic plate, and its handle part attached to a fixed metallic circle á. Adjacent to this graduated wheel is attached a fixed index B-by means of

which every fraction of a turn made by the wheel, and conseM

quently the screw itself, may be easily discriminated. The nut

E, through which the screw plays, is attached to an iron rule The vernier being thus constructed as already described, let CD, which moves with the nut by a motion parallel to the axis us explain the manner of its application. Suppose it was desired of the screw, It is upon this rule which is fixed the object to measure the length of an object m N. We place it as repre- m n intended to be divided. Lastly, the table is supplied with sented in the figure upon the great rule, the long axis of which two brass grooves perpendicular to D c, and upon which moves corresponds with that of the body to be measured, and we the slide-rest k, armed with the steel graver o. find that its length equals four units plus a certain frac. The machine being arranged according to the description tion. To value the amount of this fraction is the object of just given, two different cases may present themselves. Either the vernier. This is accomplished by sliding the vernier the rule m n has to be divided into equal parts of a determinate along the length of the fixed rule, until the end of the vernier length--for example, four hundredths of an inch-or it may corresponds with the end m n of the object to be measured. have to be graduated into a given number of equal parts. Under This adjustment being made, we next seek for the point of the first conditions, the course of the screw, or its length from coincidence hetween the divisions of the two rules. In the thread to thread, being equal to one hundredth of an inch, tho

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operator turns the circle a through one-fourth of an entire revo- substance in an apartment the air of which is frequently lution, engraves a mark on the rule, then turns the wheel through renewed. another fourth of a revolution, engraves another mark, and so Another example of the extreme divisibility of matter, even proceeds until the operation is completed. Under the second when organised, is furnished by the globules of the blood. conditions, let us suppose the division of the rule mn into Blood is made up of red globules, floating in a liquid termed eighty equal parts to be the problem for solution. The serum. In man, these globules are spheroidal, and their diaoperator now commences by causing the screw to turn in meter only amounts to about the .0003tb part of an inch. the direction from right to left, as relates to our diagram, Nevertheless, the particle of blood capable of being taken up until the extremity m exactly coincides with the point of the on the point of a needle contains nearly 1,000,000 of such graver; then reversing the direction of rotation, and causing globules. But, what is more wonderful still, certain animals the wheel to move from left to right, in relation to the diagram exist so amazingly small, that they can only be seen by the aid until the other extremity n of the rule corresponds with the of a microscope of high power. They move about as large point of the graver. The operator counts the number of turns, animals do; they are nourished; they possess organs; how

Fig. 2.

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and the value of the fraction of a turn, if such exist, gone | immeasurably small must those particles be of which such through by the graduated wheel in causing the rule co to animals are composed ! advance from one extremity of the object mn to the other. The divisibility of any kind of matter having been pushed Then, dividing the total number of revolutions by 80, the so far that its particles are altogether imperceptible, even by quotient indicates the space along which the screw z must the aid of the most powerful microscope, experiments can advance for each both of mn. It only now remains to engrave no longer determine whether such matter be finitely or a mark on mn at the cessation of each partial revolution of infinitely divisible. Nevertheless, the stability of chemical the wheel.

properties belonging to each kind of matter, the invariability Divisibility. This is the property which all bodies possess ments, and other important considerations, point to a

of relation subsisting between the weights of combining eleof being susceptible of division into distinct parts. Numerous belief'in a finite limit to material divisibility. Circumstances examples might be cited illustrative of the extreme divisibility of this kind have led philosophers to assume that bodies are of matter. Thus one grain of musk is sufficient to evolve constituted of material elements not susceptible of division, during many years the peculiar odorous particles of that and to which, therefore, the term atoms is applied.

LESSONS ON CHEMISTRY-No. II.

latter is by far the more convenient plan of the two. I have Taking up the subject at the point where we left off in our

not assumed the student to possess a cork-borer, but I will last lesson, the reader will remember that he must perform

describe the instrument, so that it may be made or procured at certain operations on certain corks. He must then adapt these such as is employed for the

ferrules of fishers

rods, of equal size

once if convenient. It merely consists of a piece of brass tube, Florence flask, in such a manner that two instruments may be with the hole to be bored, and sharpened by filing to a rough formed as represented in the diagram annexed.

Baw-edge at one end. If a transverse hole be bored through

the brass tube towards the other end, all the better : the conFig. 1.

Fig. 2

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The four-ounce bottel with its tobacco-pipe attachment, will not be required just now, but we shall speedily want it, therefore let the arrangement be made at once. Now the treatment of the cork involves two separate pr cesses, boring and external fitting, and the order in which these operations are performed is not immaterial. The boring operation must come trivance permitting the insertion of an iron wire as represented first. There are two methods of boring a cork; either by by a, thus attaching to the instrument a sort of gimlet handle, thrusting a pointed red-hot wire through it, and afterwards and conferring that kind of additional power which mechanics accurately enlarging the orifice by means of a rat's-tail file, or term for the sake of brevity“ purchase," :—with such an instruby the we of a special instrument tèrmed a cork-borer. The ment as this, cork-boring is a very simple affair. A cork-bore, being taken of the proper diameter, its edge is sharpened by a it remains to attach the length of India-rubber tubing to the few rubs of the file, and pressed against the cork under con- tobacco-pipe shank, and a few inches of glass tubing to that of tinuous rotatory motion, when it soon penetrates through the India-rubber, so that eventually an apparatus may result of the central core, escaping through the tube itself. As there is following shape, where a represents the point of attachment some little chance, however, that the side of the cork where the between the India-rubber tube, and tobacco-pipe shank; and hole emerges may assume a ragged aspect, it is better to commence the operation at one end of the cork, then without

Fig. 4. penetrating quite through withdraw the borer, and recommence at the other end, thus causing the operation to terminate in the middle. If the aperture be clean and smooth it may be considered finished ; if it be rugged and uneven, how. ever, it will require trimming with the rat’s-tail file. The aperture being made, we now come to the insertion of the tobacco-pipe shank, a matter of much simplicity ; one would think that no special instructions were necessary. It is not 80 :-the operation requires to be set about in a systematic way; and although in this case, the operator might succeed after many attempts, and tobacco-pipes being cheap enough, these numerous attempts might be made without the objection of great expense; yet considering the necessity for performing similar operations under modified circumstances to which the a'the point of attachment between the latter, and the associated objection of expense and many others would strongly apply, glass tube. Perhaps it is scarcely necessary to indicate that it is better to cultivate the right habit at once. Remember, round or oval glass flasks will not stand upright without some then, tobacco-pipes and glass tubes are not like metal rods. kind of support; they may require to be supported whilst exWe cannot fit them tightly, by violently twisting, turning, and posed to heat or after removal from heat. In the former case pushing, nevertheless we must fit them air-tight. Our object rings or triangles are usually employed, attached to a vertical is accomplished by easing them in, to use popular but an stand, and capable of elevation or depression (fig. 5). Instruexpressive word. Their accuracy of adjustment is secured by ments of this kind can be procured ready made, but every paying attention to various little circumstances of detail. If, experimenter possessed of moderate ingenuity can prepare them then, the end of the tobacco-pipe shank be ragged, as it most or their substitutes for himself. A carpet-rod, around one likely will be, rub off those ragged inequalities by means of a extremity of which has been cast a block of lead, answers per. file. Had we been concerned with a thin glass tube instead fectly, and the rings may be made of stout iron wire, as of a tobacco-pipe, the better plan of treatment would have represented in fig. 6. consisted in melting the extreme end of the same by holding it for a few instants in the fame of a spirit-lamp or a jet of

Fig gas.

Fig. 3.

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Our present operations having reference to clay, not glass, we have not this resource; but on the other hand a tobacco

An examination of the mechanical conditions to which the pipe shank is stronger than a glass tube, in consideration of wire ring is subjected will prove that it requires no screw or which I have chosen it, otherwise a piece of glass tube would other contrivance for fixing, when moderate weights have to have answered the purpose equally well.

be supported. Having finished the attachment of the tobacco-pipe shank,

Matters are now ready for the commencement of our operawe now come to the attachment of the cork itself, which is tions. The subject of this lesson is zinc, but it is iron which effected by accurate filing, a slightly conical form being im- must first claim our attention. We require to effect a combiparted to the cork, in order that it may tightly fit with the nation of this metal with sulphur, in order that something may minimum of pressure. This precaution is especially requisite be made wherewith certain properties of the zinc may be when a thinnecked flask has to be corked. In this case a tested. The combination of sulphur with iron is called sulvery slight amount of pressure will infallibly break the neck phuret of iron, occasionally the sulphide of iron, and let the uf the flask.

reader well remember that The cork I will now assume to have been accurately adapted, oy filing, to its orifice; but it is hard and rigid. Corks may be A SULPHide

A SULPhrte softened by immersion in boiling water, a treatment which

is not will answer all present ends; but cases frequently present A SULPH vret

A SULP Hate. themselves when a cork, forming part of a chemical apparatus, must be absolutely dry, under which circumstances it must be the termination ide or uret express the same compound, but the softened by immersion in hot sand, or more extemporaneously, terminations ite and ate express two different compounds ; dif. but less rapidly, by holding it for a few seconds in the fame ferent not only as materially between themselves, but as of a spirit-lamp. Having completed the arrangements to the extent described,

• The a to the right in the cut should be d'.

or

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or a

between themselves collectively and a sulphuret or sulphide. a proper substitute must be found to take its place, and henco What is the difference ? No matter. That point will come under the terms water-bath, oil-bath, &c. consideration by-and-by; we are not now treating of sulphur compounds, but of the metal zinc. If the collateral facts just

Fig. 7. mentioned choose to attach themselves to the learner's memory, well and good ; if not, let them pass, they will be made to attach themselves in the sequel. Sometimes, however, when one gives a collateral fact on the understanding that it may stick

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A sand-bath consists of an iron dish (a saucepan answers very well) containing sand, and hung or rested over any convenient source of heat. A few pieces of lighted charcoal supply a very convenient source of heat; and by putting the lighted charcoal into a perforated earthenware flower-pot, strengthened by banding with copper or iron wire, we gain all the advantages of a furnace; a temporary grating may readily be made of strong wire, and the pots, pans, and other vessels to be heated may be supported on triangles of hoop iron, fig. 8.

Plg. 8.

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in the brain or take flight just as best suits its own good pleasure, it sticks there all the firmer. I always give collateral facts an option of this kind. To effect the union of sulphur with iron, in other words, to make sulphuret of iron, it is merely necessary to bring a white-hot bar of iron in contact with a roll of sulphur; then the iron drops into melted globules which seem like iron itself, but which in reality are a compound of iron and sulphur, and weigh heavier than the iron by the weight of the sulphur where with they have combined. The greater number of metals can be made to combine with sulphur, by a similar treatment to that now described, and, indeed, perhaps the act or combination just effected may have presented itself to the reader's attention under the aspect of natural magic. To melt a nail in a walnut-shell, is a proposition often constituting the subject of a wager. The learner now sees The preceding diagram represents a furnace of this kind, how that wager might be won. A nail being heated to white which may be worked on a table, the latter being protected ness, is dropped into a walnut-shell containing sulphur, when from heat by the intervention of a Welch tile or flat stone. Prothe fusion of the nail immediately takes place.

bably the furnace will crack, owing to the intense heat Let the sulphuret of iron thus resulting be transferred to a within. It is, however, none the worse for this accidentbottle labelled Sulphuret of Iron, and put away,—we shall the binding wires prevent all separation between the various require it presently. We will now return to the zinc solution, pieces of which the furnace is composed ; and, in short, the which has been so long neglected that the student may fear furnace is no less useful than before. the original subject of the lesson has been forgotten. Not so. Supposing the solution of zinc in oil of vitriol and water to Every point expatiated on, everything done, has had reference be placed in a saucer or porcelain dish, specially made for the to the metal zinc.

purpose, under the name of evaporating dish ; supposing the I have already said that the metallic zinc employed remains solution and its dish to be embedded in the sand-bath, and in the solution; the next point, then, is to ascertain the con the latter placed on its hoop-iron tripod over a fire, heat will ditions it has assumed, and this information may be obtained rapidly penetrate the sand, and evaporation will ensue. If by driving off the liquid in which it is dissolved. This is the solution were to be evaporated very slowly, the saucer or accomplished by the application of heat, which, causing the pan would eventually contain white crystals. If, however, liquid to become steam or vapour, the latter is driven off, and the evaporation be more rapidly pushed, then crystals do not all bodies contained in the liquid, not capable of assuming appear, but a white confused mass. I suppose the latter to this vaporous condition, necessarily remain.

be the case. As soon as evaporation is complete, and the The application of heat in many processes of evaporation residue has become thoroughly dry, remove the saucer from and distillation requires many precautions. For the most part the sand-bath, allow it to cool, and when cold dissolve the naked fires are ineligible; frequently a sand-bath is the best evaporated material in distilled water. The liquid now returns means of applying heat, and it is the source of heat we shall to the state in which it originally was before evaporation, with employ now, fig. 7; but occasionally the heat capable of this difference, any excess of oil of vitriol over and above the being imparted by sand would be injuriously high, hence quantity necessary to dissolve the zinc, has been driven away

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Observe now the result. The zinc solution immediately the vessel is about two-thirds full, then cause the gas to pass

Pour into the four-ounce phial cold distilled water, until deposits a white powder, and no other metal, except zinc, wouid, tender the conditions of our experiment, have deposited a white through it in bubbles – the operator agitating the bottle frepowder. Thus arises a most important addition to our know- quently, fig. 11. Continue the operation until the water refuses ledge concerning zinc. To obtain this white powder, which to dissolve any further portion of gas, which may be known by is called sulphuret of zinc, being a compound of sulphur and removing the bottle from the table on which it stands ; grasp it zinc,—to obtain this white compound, I say, is the object to If the water be not yet satisfied, it will endeavour to suck in

firmly, pressing the thumb against its mouth; agitate briskly. which all our care and attention have been directed-all our the thumb, fig. 12. Give it, therefore, more gas, and when cork-boring, and furnace-making energies, brought into play.

Perhaps some chemical beginner may think the result fully charged, label it thus—"Hydro-sulphuric Acid Solution,” hardly justifies the trouble with which it has been achieved. | and set it aside, fig. 13. Not so ; the result is all important, as will soon be perceived.

Fig. 12.

Fig. 13, One instance of its importance, slightly anticipating another part of our subject, I will now give.

Zinc is readily thrown down out of its solution in oil of vitriol and water, by transmitting through it a current of sulphuretted hydrogen gas, as we have seen. Most other metals are also capable of being thrown down by this gas, but iron is one of a few exceptions. Hence, supposing iron and zinc had both been dissolved in oil of vitriol and water, and the proposition had been to separate the iron from the zinc, this might readily have been effected by pouring through the mixed solution a stream of sulphuretted hydrogen gas, which would have thrown down the zinc, but left the iron.

We have not quite left the zinc yet. We shall return to it hereafter; meantime, let the wine-glass be labelled “Sulphuret of Zinc," covered with a pane of glass to protect it from dust, and set aside, fig. 10. Fig. 10.

LESSONS IN ENGLISH.-No. LXVII.

By John R. BEARD, D.D.

AGREEMENT OF THE SUBJECT AND VERB.
SULPHURET

While the subject of a proposition may agree with a qualifying

adjective and a limiting or defining article, it specially agrees with ZINC

the verb. The agreement is of two kinds, one of form, another of substance ; one flexional, another logical.

We may express these facts differently, by saying that if the verb is in the plural number, its subject must be in the plural number; and if the subject is in the plural number, in the plural number must the verb be. In other words, both subject and verb take the same condition; and this is what I mean by stating that the subject and the verb must agree. Avoid, therefore, the error common with uneducated people, of joining together subjects and verbs of different numbers. This error most commonly consists in

omitting the s where it should be placed, namely, in the third perThe student will have noticed that the sulphuretted hydro- namely, in the third person plural. I subjoin the present tense

son singular, and putting the s where it should not be placed, gen, or hydro-sulphuric acid gas, by which the throwing down in its

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