Εικόνες σελίδας
Ηλεκτρ. έκδοση






according to the cases with which they are construed. Some of scription, six penny stamps, which we have sent to the Rev. Mr. them are construed with the genitive only; some with the Curwen, of Plaistow, in Essex, who wrote the appeal on the lady's dative only; some with the accusative only; and some either behalf, and who alone is in communication with her, is a sufficient with the dative or accusative, according to circumstances.

proof that the letter and the transaction which it so simply, yet

beautifully, describes, are real and not fictitious.] (2) They may also, on a different principle, be divided into two general classes: the Primitive and the Derivative. The primitive prepositions always govern either the dative or the

ANSWERS TO CORRESPONDENTS. accusative: the derivative prepositions are found, for the most part, in connection with the genitive only.

UN INGENIERO CIVIL: Try Nesbitt's Land Surveying or old Croker. ELITERA should apply to the minister or curate of his parish.

T.H. (Workington) must apply at the Herald's office; we can't assist

him.-A TYPO (Darlington): Yes.-ELEMENTARY (Newcastle) must look CORRESPONDENCE.

more narrowly at our later numbers,

OLD SUBSCRIBER (Limehouse) will find it necessary to buy blank books

for bookkeeping, cheap, as he says, and rule them himself. INDUSTRY AND CHARITY.

UN ETUDIANT FRANÇAIS (Guernsey): The sections referred to in the

French were omitted as useless.-E. WARREAT (Bristol) and J. E. S. A.: widow hath cast more in, than all they who have cast into the Their kind suggestions will be kept in view.-R. M. H.: Vols. i., il., treasury.”-Mark xii, 43.

iii. of the P. E. are bound separately, and the cheapest may be had for

3s. 6d. each. SIR,This evening we received our weekly allowance of mental H. GUY (Moorsley): His " Remarks on the Study of Grammar" are very food in the shape of the POPULAR EDUCATOR, with one or two well written. Let him persevere, and he will greatly improve.-J. P. minor publications, which we use as sauce for goose and gander; (Shepwyke) : We should be very glad to oblige him, but the lines he wishes or, rather, to amuse us in the evenings, after the study of the to be inserted are an advertisement.-J. HALL (Hyde): See Errata, p.

When two volumes of pure hydrogen gas are mixed with one volume of English, Latin, and other lessons, that the P. E. provides for us.

pure oxygen gas, and the mixture inflamed in a proper apparatus by the Weil, sir, I have said that we obtained your paper this evening, electric spark, the gases totally disappear, and

the interior of the vessel is and, as is generally the case, whilst my wife is busily engaged in

wife is busily engaged in covered with drops of pure water, equal in weight to that of the gases conclearing the tea-things from the table, I take the EDUCATOR and sumed."-Brande's Chemistry. look down the outside columns of it, so as not to lose one morsel S. CLARE (Ashton-under-Lyne): His remarks on the asymptotic paradox of the knowledge which is often elicited from you by some question. are very excellent, and we would insert them if we had room.-W. WARD ing correspondent who has been kind enough to ask for the very (Stepney) and W. B. Hodson (Lincoln): The questions are very old, and thing I wanted. I have learnt some good precepts, some useful Received.-R. T. s. 0. (Bromley) should study English belore Bookhints, in this manner, without in my way of thinking) losing keeping. time.

E. T. B. P. (Liverpool): We have made no errors in the Map of France; You must know, sir, that my boys attend the day-school in our for we consider the Chief Torons as those which have the largest population, village, where, amongst other things, English grammar and com- and not those which are appointed so by any government wiateier!!-OLD position are taught. These are favourite studies with my boys; so

BOB (Queenshead) is too technical for us. that you will suppose I (who never knew English grammar before

JOHN CUNNINGHAM (Liverpool): In our lesson on the impressions of I studied the P. E.) am obliged to make the most of my time to rain-drops on the surface of sandstone, we ascribed the discovery of these keep pace with them; for I like not the idea of my boys learning he who first observed these impressions, and that it was he who first called that of which I (their father) know nothing. On scanning the Dr. Buckland's attention to them. He does us the justice to say that we column of Correspondence, I saw your kind-hearted appeal to us, robbed him of this honour " unintentionally.” We are, therefore, happy in behalf of an unfortunate lady who is behind-hand with thé in having this opportunity of correcting our error, and of giving to him P.E. I immediately proposed the following question :--"Who the palm which he has so well deserved. will vote for the selling of the P. E. for the purpose of getting together, one hour an evening, and you will get on.-J. Robins should study

ENRICE L. FILLIPE (Stamford-street): Study Italian and English some plum-cake at Christmas ?Not a voice !

our lessons in Penmanship and English Grammar, and his difficulties will better for us, to have plum-cake or the POPULAR EDUCATOR?"

disappear. “EDUCATOR," cried three voices at once. Well, then, said I, a

L. FERNANDEZ (Oldham) wants to know our opinion of an exceedingly poor lady is in want of some help, so that she may be enabled to bad sentence in English, and whether there be any treatises on woollen purchase the remaining numbers which she has not in her pos- cloth and on ventriloquism !!--J. B. (Manchester): You are learning session. I then proposed this resolution : that we make a sub- the very system that the American minister recommeuds, viz., Ollenscription of one penny each, to send to the editor, for the benefit dorf's. of this poor lady

JAMES RUSSELL (44, Meadowside, Dundee) very kindly offers to give

assistance gratis to the students of the POPULAR EDUCATOR who reside The boys went each one for his saving-box; I think, sir, you in his neighbourhood, in Cassell's Arithmetic, Algebra, and Euclid; between would have smiled to see their alacrity; the penny each was placed the hours of 5 and 7 P.M., or 9 and 10 P.. We feel assured that many of on the table, my penny with theirs. My wife gently hinted the our readers in Dundee will most gladly avail themselves of this generous impracticability of sending pence, and proposed the making up of offer. the sum to sixpence, which could go in a note; for, said she, MRS. SLIPSLOP (Aberfeldy): We thank her for the loan of her spectacles, though we have enough to do to make both ends meet, we are not they are better than ours; whether the printer's pair or ours were in fault, unwilling to give to a good cause. She is willing, I assure you, correction. The error has arisen thus : there are two Nahors in Genesis

it is now too late to determine; but we are glad to make the necessary I heard her say, not long since, she would make a half-pound of xi., viz., one in v. 22 and 23, and another in v. 26, 27, and 29; the one was sugar serve us for a week, rather than that her husband should go the father of Terah, and the other his son ; the former has been, by some without the P. E.

unaccountable mistake, omitted in our table, p. 3, vol. i. We hope the unfortunate, but well-deserving object of your ap- E. BYRT (Shepton Mallet): Yes.-ROBERT HUMBLE (Hartlepool): The peal will succeed in her praiseworthy exertions; and by some laws of the resistance of the air to falling bodies will hereafter be conmeans be placed above the necessity of studying at such a dis- sidered. The rule for finding the height of a tower, as usually given, is, of

course, not strictly correct. advantage. She will surely thank you for your kind-hearted hint, which we hope will be met by as kind a sympathy by very many of Charlottensquare, Edinburgh. Tur Pencil (Paddington): We are just

G, ASPINALL (Liverpool): Apply to Mr. Bell, 13, South Charlotte-street, our fellow-Christians. We would that ours was a larger sum; thinking of the students of the pencil, and mean to do something soon. bat, sir, we give a little and wait. If we hear from you again-as J. R. M. (Glasgow): See col. 1, p. 376, vol. iii.--AMATOR SCIENTIR (Dundee): my boys are saving their money for an Easter holiday-we will raise We prefer Bell's system to Pitman's.-H. HALES (Southwark): 'We doubt another subscription. I beg you to look down from your learned much whether he would succeed in the business of making cheap apparatus eminence, and spare, or gently point out, the errors of your pupil, and selling it himself. He had better apply to our friend Mr. J. Griffin, of who is


Finsbury-square, and see what can be done there.

ISAAC NEWTON (Sheffield): Our friend with this glorious nom de guerre P.S.--My boys are longing to see the letter which, say has not so sustained the credit of the name as to admit of the insertion of they, father is writing to the editor of the POPULAR EDUCATOR. his solution of the boy and apple question !!--W. E. WILLIAMS (PentreDecember 7th, 1853.

bach): The lessons in English are closed for the present; as soon as possible

Elocution will be taken up.-G. S. (Cupar): We know of no such book as a [We hope that our readers will be as much pleased with this treatise on Greek pronunciation.-W. WALLIS (St. Ninian's): Mr. Bell did letter as we have been. It does much credit both to the head and not say that his « Vocabulary of Syllabic Logograms" was to be inserted in the heart of the writer, as well as to those of his amiable family. the P. E.; you have, therefore, no right to expect them in our pages.

Several correspondents have committed this error. We can assure the most critical of our readers that it is a genuine production, and not got up for the sake of puffing the P. E.--a thing of which we have been most unjustly accused. We have not

Tol, iv., p. 155, col. 1, line 10 from bottom, for insolubility read the most remote idea of the author or of his locality ; but the sub-! po bability.


When the exterior air is re-admitted into the receiver by ineans ON PHYSICS OR NATURAL PHILOSUPHY.

of the proper stop-cock, the bladder is again compressed by it, No. XVII.

that is, reduced to its former dimensions, the equilibrium being

restored. In the same manner, we may easily prove the fact (Continued from page 235.)

of the expansive force of all the gases. PNEUMATICS,

In consequence of its expansive force, it seems as if any gas

contained in an open vessel would make its instantaneous GASES AND THE ATMOSPHERE.

escape. Such indeed is the case, if the vessel be placeä in a Physical Nature of Gases.-Gases or aeriform fluids are bodies vacuum; but, in ordinary circumstances, the pressure of the whose particles possess perfect mobility, and which are in a exterior air is opposed to the issue of a gas from the vessel. It constant state of repulsion called expansibility, tension, or elastic can be proved indeed, by experiment, that an equilibrium can force; in conformity with the latter of these appellations, be made with the expansive force of any gas, only by the gases are frequently denominated elastic fluids.

counteracting pressure of a gas of the same nature as itself. The elastic fluids are divided into two classes, Ist, the per, the expansive force of hydrogen or carbonic acid. These gases,

Thus, the pressure of the air cannot make an equilibrium with manent gases, or those which are properly called gases ; and however, do not escape into the air from

the vessels containing 2nd, non-permanent gases, or vapours. The former are those them, as they would in a vacuum ; but the interior and which maintain the aériform state under any pressure or exterior fluids are rapidly mixed together, as we shall see in diminution of temperature, as oxygen, hydrogen, nitrogen, the sequel. It will then be shown that the elastic force of binoxide of nitrogen or nitric oxide, and carbonic oxide. The gases is always equal and contrary to the pressure whịch they non-permanent gases, on the contrary, easily pass into the liquid state, either by strong pressure or by lowering the support, and that it increases with their temperature. temperature. This distinction, however, is not rigorously Process of collecting Gases. A great many gases being colour. correct, for a great number of gases, which were considered less, inodorous and insipid, do not fall immediately under the permanent, have been liquefied by Faraday and others, and it cognisance of the senses, like solids and liquids ; but they must be admitted that those which have not hitherto been become apparent by the processes employed in collecting them. liquefied, would be so if they were subjected to sufficient pres- Suppose, for example, that it was required to get hydrogen, a sure, or lowering of temperature. Gas, therefore, is the name gas which forms one of the elements of water. * We take a double applied to bodies which, under ordinary pressures and tem. mouthed bottle B, fig. 63, furnished with two tubes, and intro peratures, exist only in the aeriform state ; whilst vapour is

Fig. 63, the erm applied to the aeriform state which bodies take under the application of heat, bodies which, like water, alcohol and ether, exist in a liquid state under ordinary pressures and temperatures.

In chemistry, the gases at present known are 14 in number, of which 4. are simple, viz. oxygen, hydrogen, nitrogen, and chlorine; 7 are found in natural productions, viz. oxygen, nitrogen, carbonic acid, protocarburetted hydrogen (marsh gas) and bicarburetted hydrogen (olefiant gas), ammonia and sulphurous acid. All the other gases are only obtained by chemical processes.

Expansive Force of Gases.The expansive force of gases, that is, their tendency always to assume a greater volume, is proved by the following experiment. Place

under the receiver of an air-pump a moistened bladder furnished with a stop-cock, and containing a quantity of air. At first, there is an equilibrium between the elastic force of the air in the receiver and that of the air enclosed in the bladder ; but as soon as the exhaustion duce into it, & certain quantity of water and of granulated of the receiver commences, the pressure on the bladder is zinc; one of the tubes, which is upright, is furnished with a diminished, and it swells or expands, as the process of funnel by which the sulphuric acid is introduced, necessary to exhaustion advances, just as if it were infiated by the addition the chemical reaction which produces the hydrogen. The of a greater quantity of air ; this expansion proves that the air other tube, which is bent, conducts the gas as it is produced, which it contains possesses an elastic force; see fig. 62. into a bell-shaped glass or inverted bottle a, filled with water

and placed in a vessel full of the same liquid. Fig. 62.

Fig. 64.

[ocr errors]
[ocr errors]
[graphic][ocr errors][merged small]
[ocr errors]

By the mutual action of the zinc and the sulphuric acid, points, and acts with equal force in all directions. As to the the water in the bottle is decomposed; its oxygen is united pressure arising from the action of gravity, it is regulated with the zinc, and the sulphate of zinc is produced, which exactly according to the laws of the pressure of liquids formerly semains in solution ; its hydrogen is now set at liberty, and explained ; that is, that it increases proportionally to the passes, in consequence of its elastic force, into the bell-shaped density and to the depth; that it is constant on the same glass A, where it rises to the top on account of its lightness, or its horizontal stratum; and that it is independent of the form having less specific gravity than water. The other gases are which the gaseous mass assumes. Moreover, for volumes of collected in a similar manner, but under the influence of very gas of small dimensions, this pressure is so little that the condifferent chemical reactions,

sideration of its amount may be, in ordinary cases, entirely

omitted, Transference of Gases from one Vessel to another. In the same way as liquids are treated, so gases can be poured from one vessel

THE ATMOSPHERE, into another. This experiment is easily made with carbonic acid, which is much denser than common air. Thus, we fill a Composition of the Atmosphere.--The name atonosphere is applied bell-shaped glass with this gas, by collecting it in the manner to that great ocean of air which surrounds our globe, and is above mentioned; then, taking a second vessel of the same carried along with it, in its daily and annual revolutions. The kind and size and full of air, we pour the contents of the for- air was considered by the ancients as one of the four elements mer into the latter, as shown in fig. 64, holding them for some of which all things consisted. Modern ehemistry has shown time in a fixed position. In consequence of its excess of that it is a mixture of nitrogen and oxygen, containing in 100 density, the carbonic acid descends slowly from the vessel m cubic inches of the mixture, 79.20 cubic inches of nitrogen and, into the vessel n, from which it drives out the air, so that as 20.80 cubic inches of oxygen. Moreover, in 100 ounces of air, soon as the vessel n is full of carbonic acid, the vessel m is full there are 76-99 ounces of nitrogen and 23.01 ounces of oxygen. of air. The proof of this rests on the property which carbonic The atmosphere also contains a quantity of the vapour of water acid possesses of extinguishing lighted bodies. For, before the which varies with the temperature of the air, the seasons, the experiment, a lighted taper burns in the vessel n and is extînio climates, and the direction of the winds. Lastly, the air conguished in the vessel m; whilst after the experiment the con- tains of carbonic acid in a given volume, at a mean, only about a trary is the case.

two-thousandth part. The carbonic acid is produced by the Weight of Gases.-From their extreme fluidity, and especially respiration of animals, and the combustion and decomposition of their expansibility, gases would seem not to be subject to the organic substances. According to the estimate of M. Bouslaws of gravity; but these subtle fluids obey this force as singault, there are nearly three millions of cubic metres (about well as solids and liquids. In order to prove this, suspend 660 millions of Imperial gallons) of carbonic acid produced at under the scale of a very sensible balance, a glass globe capable Paris, by these processes, in twenty-four hours; the part proof holding about a gallon of air, and furnished with an air duced by animal respiration being about one-ninth of the tight stop-cock, see fig. 65. First weigh this globe full of air ;


Notwithstanding the continual production of carbonic acid Fig. 65.

at the surface of the globe, the composition of the atmosphere does not appear to be altered by it, the reason is, that in the process of vegetation, the green parts of the vegetables decompoge the carbonic acid under the influence of the solar light, assimilating the carbon and giving back to the atmosphere the oxygen which is continually abstracted from it by the respiration of animals and by combustion.

Air being heavy, if we conceive the atmosphere to be divided into horizontal strata, it is plain that the superior strata will press on those below. them, by their weight, and the result will be the compression and condensation of the inferior

As the pressure on any stratum will evidently diminish as the number of superincumbent strata diminishes, the air is evidently rarified in proportion to its distance from the surface of the globe.

In consequence of the expansive force of the air, it would: seem that the particles of the atmospheric air should extend indefinitely into the planetary spaces. But by the very effect

of dilatation, the expansive force of the air decreases more and then, after having created a vacuum in it by means of the air- more; moreover, it is lessened by the low temperature of the pump, weigh it again, and it will be found that the weight of higher regions of the atmosphere, so that there is a point where it the second time will be some grains * less than it was the first an equilibrium is established between the expansive force of time, showing that this weight of air has been withdrawn from the particles of the air, and the action of gravity which

attracts them to the centre of the earth; hence it is concluded the glass globe.

that there is a limit to the extent of the atmosphere. By the preceding process, it has been found that 61 cubic inches of pure air at the temperature of 32° Fahrenheit, and

From the weight of the atmosphere, its decrease in density, under an atmospheric pressure of 30 inches in the barometer, and the observation of crepuscular (twilight) phenomena, its weighs 20 grains, the same quantity of hydrogen weighs 1•39 altitude is estimated at about 40 miles from the surface ; grains, or about 14 times less than air; and the same quantity beyond this limit, the air is extremely rarified; and beyond of hydriodic gas, which is the densest of the gases, weighs 89 the altitude of about 50 miles, it is considered that there is an

absolute vacuum. grains.

Since we have already stated that the air

is a heavy body, and given the actual weight of a certain The Pressure of Gases.--Gases produce two kinds of pressure, quantity near the surface, it is evident that the whole of the one on the particles of which they are composed, and another atmosphere must act upon the surface with a very considerable on the sides of the vessels which contain them; the one pro- pressure. The actual existence of this pressure is proved by ceeds from their elastic force, and the other from their weight. the following experiments. The pressure which arises from their elastic force is transmitted with the same intensity to all points of the mass of the

The Bladder Glass.--Take a short glass cylindor about 4 fluid and the sides of the containing vessel ; for the repulsive inches in diameter, ground smooth at one end, and furnished force which exists between the particles is the same at all with a bottle-lip at the other; over this end fasten a piece

of bladder, so as to be perfectly air-tight; well grease the * About 90 grains, if the temperature of the air be taken at that of ground end of the cylinder, and place it firmly on the receiver the maximum density of water, and the exhaustion be complete, plate of an air-pump, so that no air may be adinissible at the




[ocr errors][ocr errors]

odges Dext the plate, fig. 66. Rapidly exhaust the air from pump, screw on the handle at the end of it, and try to pull the the cylinder; and as soon as you commence making a vacuum, hemispheres asunder by the two handles, see fig. 68. This the bladder at the top of the cylinder will first sink under the attempt will fully convince you of the force with which the atmospheric pressure, and then burst with a loud noise, which is occasioned by the sudden re-admission of the air.

Fig. 68.

[merged small][graphic]
[ocr errors]
[ocr errors]

atmosphere presses the hemispheres together; for it will take a force of about 500 lbs. *o separate them, supposing their diameter to be 5 inches, and that the exhaustion of the air were complete. This may be proved by fastening the one handle to a beam, suspending & scale to the other handle, and loading it with weights until the hemispheres be separated. In the original experiment performed by Otto Von Guericke at Madeburg, in 1560, there were from 14 to 30 horses harnessed to the hemispheres, which were two feet in diameter, without effecting a separation; when more horses were added, the hemispheres parted with a loud report. If after the attempt to separate the hemispheres by a force less than sufficient to separate them, the stop-cock be turned so as to re-admit the

air into the apparatus, they can then be separated with the If, instead of the piece of bladder fastened to the top of the external and the internal air has been restored.

greatest ease, because the equilibrium of pressure between the cylinder, there be placed on it a square piece of thin glass made air-tight, by having this end of the cylinder also ground MEASURE OF ATMOSPHERIC PRESSURE, smooth and well greased, you will find that on the application of the air-pump to exhaust the cylinder, the glass will first

The Torricellian Experiment.—The preceding experiments bend under the pressure of the external atmosphere, and then prove the existence of atmospheric pressure, but do not break into pieces with a loud crash.

acquaint us with its amount. The following experiment made Magdeburg Hemispheres.--The bladder-glass appears only to gives the exact measure of the weight of the atmosphere, or

for the first time in 1643, by Torricelli, a disciple of Galileo, prove the existence of the atmospheric pressure vertically of its pressure on every square inch of surface at the bottom of a downwards. By means of the Magdeburg hemispheres so (named column of this size, extending to to the top of the atmosphere. from the town where they were first invented), it is proved Take a glass tube cd, fig. 69, not less than 33 or 34 inches that this pressure acts in all directions. This apparatus is composed of two hollow brass hemispheres, between 4 and 5

Fig. 69. inches in diameter, fig. 67, furnished with broad edges ground

[ocr errors]

Fig. 67.



[ocr errors]
[ocr errors][merged small]
[ocr errors]

smooth and made to fit each other exactly, so that when well greased they are completely air-tight. These hemispheres are each fitted with a strong ring or handle, and one of them is furnished with a tube which may be screwed on the plate of the air-pump, and a stop-cock to prevent the re-admission of the air. In making the experiment, first place the hemispheres together with their edges well. greased, and in close contact; screw the apparatus to the plate of the air-pump, exhaust the air from the sphere as completely as possible, tum-the-stop- long, closed at one end, open at the other, and of any convecock to exclude the air, and unscrew the apparatus from the nient diameter from of an inch to it an inch. Having placed

[ocr errors]

this tube in the vertical position with the closed end down-are inversely proportional to their densities. On the other wards, fill it completely with mercury; then, closing the open hand, if the weight of the atmosphere increases or diminishes end c with the finger or thumb, invert the tube and immerse from any natural cause, in any given place, it is evident that this end in a cup nearly full of mercury. Withdrawing then the length of the mercurial column will increase or decrease the finger from the tube at B, and supporting it with the other accordingly, hand at A, the column of mercury in the tube will sink two or Pascal's Experiments. The celebrated Pascal, wishing soon three inches, and then become stationary at a height A B of after, to prove for himself that the force which supported the about 30 inches above the mercury in the cup, when the mercury in the tube of Torricelli was really the pressure of the experiment is performed at the level of the sea, and during a atmosphere, had recourse to the two following experiments, mean state of the atmosphere.

which placed the fact beyond a doubt. First, foreseeing that In order to explain the nature of this experiment, we observe, the column of mercury ought to descend in the tube in proporthat as the pressure of the atmosphere acts with great regu- tion as it was raised in the atmosphere, because that then its larity on the superficial stratum of liquids placed in an open pressure would be diminished, he requested a relation living in vessel, it does not in general disturb the horizontality of such the province of Auvergne, in France, to repeat, on the mounsurfaces. But if by any means a limited portion of this stra- tain called Puy-de-Dome (4,846 feet high) the experiment of tum be protected from the atmospheric pressure, the equili- Torricelli. Here the column of mercury was diminished in brium will be destroyed, and the liquid will rise up to fill the height by a quantity which was between three and four inches vacuum produced above it, to a determinate height depending in length; this proved that it was really the weight of the aton the nature of the liquid. This is indeed what takes place mosphere which sustained the mercury in the tube; because, when we immerse the one extremity of a tube in water, and as this weight decreased, so did the column of' mercury. withdraw the air by suction at the other extremity. By this Secondly, Pascal repeated the experiment of Torricelli, at process, we only diminish the pressure within the tube ; but Rouen, in 1646, with another liquid instead of mercury. He in the Torricellian experiment the pressure of the air is com- took a tube of about fifty feet long, closed at one end and pletely removed, and there is a complete vacuum at the top of it open at the other; he filled it with water, and inverting it, when inverted. We have seen, that on the moment of the placed it in a reservoir full of water; he then observed that the inverted end becoming free, the mercury in the tube descends to water in the tube sunk to the level of about thirty-four feet a level about 30 inches above that of the mercury in the open above the level of the reservoir. Now the altitude of the cup; this level is always the same whatever be the length of column of water being about 13•6 times that of the column of the tube, its shape, or its inclination.

mercury, and the density of mercury being about 13•6 times In this experiment the elevated column in the interior of the periment is equal to the weight of the column of mercury in

that of water, the weight of the column of water in this extube presses on the part of the cup on which it stands, with a the Torricellian experiment; hence it is justly inferred again, force which replaces that of the atmosphere; but the latter still that it is the pressure of the atmosphere which equally supcontinues to press with the same force on the rest of the surface of the mercury in the cup; and the particles of the liquid, ports both of the liquid columns. yielding to this pressure, would have been forced up the tube to the same height, supposing that it had been a perfect vacuum, on its immersion. In fig. 70, where a section of the tube and


[blocks in formation]


DENOTE how many times a number is to be taken, as “six times six make thirty-six;" here six times is a numeral adverb; thus des signifies twice, tous three times. The termination of the numeral adverbs is in general κις (ακις, τακις), which is annexed to a cardinal, as τεσσαρακις, εξακις, εκατοντακις. .


20 εικοσάκις


[ocr errors]


1 άπαξ

19 εννεακαιδεκακις 2 δις

30 τριακοντακις 4 τετρακις

40 τετταρακοντακις OY 5 πεντακις

τεσσαρ. . 6 εξακις

50 πεντηκοντακις
7 επτακις

60 εξηκοντακις
8 οκτακις

70 εβδομηκοντακις
9 εννεακις, εννακις

80 ογδοηκοντακις
10 δεκακις

90 ενενηκοντακις
11 ενδεκακις

100 εκατοντακις

200 διακοσιακις cup is shown, it will be observed, that when the mercurial 12 dwdekakış

300 τριακοσιακις column acquires its stationary position, any horizontal stratum 13 tpiçkaideaKKLS MN, taken in the cup of mercury, supports at all points the 14 tetrapaskaidekakis Or Teocap. 1000 Xellakis

2000 διςχιλιακις same pressure ; this pressure is composed of the weight of the 15 TEVTEKAISEKAILS part a, to which must be added either the atmospheric pressure 16 ÉKKALDEKAKIS

10,000 μυριάκις without the tube, or the pressure of the elevated column within

17 επτακαιδεκακις

20,000 διςμυριακις the tube, these two pressures being equal, and capable of being measured by each other. Hence it is that the vertical height 18 OKTwkaldekakis op of a column of mercury is taken for the measure of the

RECAPITULATORY EXERCISES FROM THE CLASSICS. pressure of the atmosphere. If we perform the same experiment with any other liquid

1. Αναχαρσις κρειττον ελεγεν, ενα φιλον εχειν πολλου αξιον, instead of mercury, we must have recourse to much longer tubes, in order to produce the vacuum at the top of the column. η πολλους μηδενος αξιους. 2. Αννων, ο πρεσβυτερος, εκ της The heights to which different liquids rise, in such experiments, ΙΛιβυης επερασε μεγαλην δυναμιν εις Σικελιαν, πες, ν ε ιδας

« ΠροηγούμενηΣυνέχεια »