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Fig. 2, the valve on a larger scale, and inserted in the neck of the adapter. It consists of an internal tube of small calibre, but pretty stout in substance, and ground into an exterior tube closed at the upper end, but perforated with several small holes to allow the gass to pass. After the internal tube is ground to fit the external, a portion of it is cut out (as at a) sufficient to receive a small hemisphere of glass, and to allow the hemisphere to rise a little in its small chamber, but not to turn over in it. The upper piece of the internal tube is then thrust home to the place in which it is to remain, and the glass hemisphere introduced, with its plane incumbent on the upper end of the lower piece of the internal tube, which is ground perfectly flat, as is also the plane of the hemisphere. From the construction, it is obvious that by the upward pressure of any gass, the glass hemisphere may be raised so as to allow the aeriform fluid to pass into the adapter, but that there can be no return of any thing into the receiver, even when a partial vacuum takes place in it; and the greater the excess of the expansive force or pressure exerted at any time in the adapter over that maintained in the retort and receiver, the closer does the valve become.

Fig. 3, two adapters, A and B, ground to fit into each other, and also to fit into C of fig. 1. Any number may be fitted to each other in the same manner. By this apparatus liquids may be highly impregnated with the gasseous products evolved during distillations. The bent tube T, is for the purpose of conveying the superabundant gass to a chimney or to a pneumatic apparatus. Phil. Mag. xi. 256,

6. Methods of measuring the volumes of gasses -For this purpose we ought to be provided with several graduated glasses or jars, of different sizes, and even several of each size, in case of accidents. The manner of graduating them, as recommended by Lavoisier and others, is very easy; care being taken to secure accuracy, which is indispensable. Take a tall narrow glass jar, and having filled it with water, place it upon the shelf of the pneu. matic cistern: we ought always to use the same place throughout this operation, that the level of the shelf may always be exactly similar, by which almost the only error to which this process is liable will be avoided. Then take a narrow mouthed phial, holding exactly 5 ounces, 2 drams, 12 grains of water, which quantity corresponds to 10 cubical inches. If you have not one exactly of this capacity, choose one a little larger, and reduce it by dropping in a little melted wax and resin. This phial serves the purpose of a standard for gauging the jars. Make the air contained in this bottle pass into the jar, and mark exactly the place to which the water has descended; add another measure of air, and again mark the place of water, and so on, till all the water be displaced. It is of great consequence, that, during the course of this operation, the bottle and jar be kept at the same temperature with the water in the cistern; and for this reason, we must refrain as much as possible from keeping the hands upon either, or, if we suspect they have been heated, we must cool them again by means of the water. The height of the barometer and thermometer during this experiment is of no consequence. When the marks have been thus ascertained upon the jar for every ten cubical inches, we engrave a scale upon one of its sides, with a diamond pencil. In the same manner, glass tubes are graduated for using in the mercurial apparatus, only they must

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be divided into cubical inches and tenths. bottle used for gauging these must hold seven oz. one dr. 15 grains of mercury, which exactly corresponds to a cubical inch of that metal.

Thus prepared, let us suppose that, after an experiment, there is a residuum of gass contained in the upper part of the jar standing on the shelf of a pneumatic apparatus, of which we wish to as certain the quantity; we must first mark the height to which the mercury or the water rises in the jar, with great exactness, by means of slips of paper pasted round the jar. If we have been operating in mercury, we begin by displacing the mercury from the jar, by introducing water in its stead. This is readily done by filling a bottle quite full of water, stopping it with the finger, turning it up, and introducing its mouth below the edge of the jar, then, turning down its body again, the mercury by its gravity falls into the bottle, and the water, rising in the jar, takes the place occupied by the mercury. When this is accomplished, pour so much water into the cistern as will stand about an inch over the surface of the mercury; then pass the dish BC (Fig. 2. Pl.77) under the jar, and carry it to the water cistern already described. Here let the gass be transferred into another jar graduated as above described, which will immediately shew its volume. Another method is to turn up the mouth into the marked jar, from which the gass has been liberated, as above, and then to pour in as much water as will reach exactly to the mark made for the gass; by weighing the water carefully, the volume of gas it contained before may easily be determined, allowing at the rate of 1728 cubical inches for each 75 84 pounds troy of water. In experiments where great accuracy is required, the results obtained by these methods will need correction; in the first, with respect to the height of the barometer and thermometer; and in the second, beside the former correction, for the difference between the surface of the water in the cistern, and the height to which it rises in the jar. For the more expeditious and accurate admeasurement of the volumes of gasses, various instruments have been contrived, some of the principal of which are described under the word GASOMETER, which is the general term applied to the apparatus.

7. To determine the absolute gravity of the different gasses.--Take a large balloon A, Pl.79, fig. 4, capable of holding 17 or 18 pints, or about half a cubical foot, having the brass cap be de, strongly cemented to its neck, and to which the tube and stop-cock fg, is fixed by a tight screw. This apparatus is connected by the double screw represented separately at fig. 6, to the jar B C D, fig. 4, which must be some pints larger in dimensions than the balloon. This jar is open at top, and is furnished with a brass cap bi, and the stop-cock m. One of these stop-cocks is represented separately at fig. 5. We first determine the exact capacity of the balloon, by filling it with water, and weighing it both full and empty. When emptied of water it is dried with a cloth introduced through its neck de, and the last remains of moisture are removed by exhausting it once or twice in an air-pump. When the weight of any gass is to be ascertained, this apparatus, is used as follows: Fix the balloon A to the plate of an airpump, by means of the screw of the stop-cock fg, which is left open; the balloon is to be exhausted as completely as possible, observing carefully the degree of exhaustion by means of the

barometer attached to the air-pump. When the vacuum is formed, the stop-cock fg is shut, and the weight of the balloon determined, with the most scrupulous exactitude. It is then fixed to the jar BCD, which we suppose placed in the shelf of the pneumatic apparatus; the jar is to be filled with the gass we mean to weigh, and then by opening the stop-cocks fg and lm, the gass ascends into the balloon, whilst the water of the cistern rises at the same time into the jar. To avoid very troublesome corrections, it is necessary, during this first part of the operation, to sink the jar in the cistern, till the surfaces of the water within and without the jar exactly correspond. The stop-cocks are again shut, and the balloon, being unscrewed from its connection with the jar, is to be carefully weighed; the difference between this weight and that of the exhausted balloon, is the weight of the gass contained in the balloon. Multiply this weight by 1728, and divide the product by the number of cubical inches contained in the balloon, the quotient is the weight of a cubical foot of the gass submitted to experiment. Exact account must be kept of the height of the barometer, and of the thermometer; and from these the resulting weight of a cubical foot is easily corrected to the standard pressure and temperature; the small portion of air remain ing in the balloon after forming the vacuum, and which is readily indicated by the air-pump barometer, must also be taken into the account: thus, if that barometer remain at th part of the height it stood at before the vacuum was formed, we conclude that only of the gass was transferred from the jar into the balloon. See Lavoisier's Elements of Chemistry: a work as remarkable for the accuracy of its descriptions, as for the excellence of its philosophy.

Perolle, Priestley, and Chladni, have made some very curious experiments and observations on the tones produced by an organ pipe, and other sonorous bodies, in different kinds of gass. For the influence of gasses in promoting or retarding the growth of seeds, &c. see GERMINATION and PHYSIOLOGY Vegetable.

GASS-HOLDER, a vessel for receiving, retaining, and transporting gass. Several contrivances for this purpose have been made by different chemists. Fig. 1. Pl. 79, represents the gassholder invented by Mr. Pepys, jun. from a suggestion of Mr. Watt's: it may contain from two to ten gallons. G refers to that part of the vessel which is to contain the gass. R the register tube; the ends of which are cemented into two tin sockets by cocks at the top and the bottom of the gass-holder, into which it opens at both ends: of course the level of the water in the apparatus will always be seen in the tube, and consequently that of the gass. C, the circular cistern, with its two cocks and pipes, marked 1 and 2. C, a brass cock on the side, with a screw, to which bladders or a blowpipe may be attached. O, an opening into the gass-holder, in which a pipe is soldered, at such an angle, that, when all the uppermost cocks are shut, no water can possibly escape. But, when a conducting-pipe, from a retort or other apparatus generating gass, is introduced into this opening, then, as the gass passes up into the gass-holder, an equal quantity of water will be discharged at O, into any vessel fit to receive it. Sp, a spout on the side of the cistern to enable the operator to add water, even when the receiver fills its whole area. H H, handles to lift the gass-holder by. Re, a glass deflagrating re

ceiver standing in the cistern. A, its adopting cork and cock. To make use of this apparatus, first fill the gass-holder with water, by closing the opening O with a cork, and also the cock C, and keeping the circular cistern full of water, while the cocks 1 and 2 are both open. The air is driven out of the gass-holder through the cock 1, by the water descending into it by the cock 2. When full, the water in the register will be on a level with the top of the gass-holder. Then shut the cocks 1 and 2. You may now remove the cork from the opening O, which is then prepared to receive the conducting-pipe from any apparatus from which the gass is generating. As the gas is delivered the water escapes, and should be caught in any convenient vessel. The register will then show the quantity received: when full, close the opening O with a cork wrapped in leather, which prevents the communication with the atmosphere. It may now be easily removed or conveyed where it is wanted.

When it is required to fill a glass receiver, as c, with the gass, having previously filled the circular cistern with water, place it in the cistern, put in the adopting cork A, and with the mouth applied to the cock,exhaust the receiver, in which the water will rise till full. Then close the cock A, and open the two cocks 1, and 2, and the gass will ascend into the receiver, while the water will take its place in the gass-holder. Bladders mounted with cocks may be filled with gass, by first emptying them of air, then screwing them to the cock C, filling the cistern with water, and opening the cock 2. In all these cases the quantity used may be ascertained, which has a scale of pints or cubic inches, attached to it, and thus far answers the purpose of a gassometer. Mr. P's apparatus is also adapted for combustion, deflagration, and other experiments with the gasses, as well as for the use of the blow-pipe. In these cases, the following additions to the original instrument are highly useful. S, a watch-spring in a slit wire, prepared for combustion. D, a deflagrating dish of iron, for sulphur, phosphorus, sugar, &c. &c. B, a blow-pipe, with a gum-elas tic tube E, capable of joining the cock C k.

For simply retaining and conveying the gasses, when it is not necessary to ascertain their quantity, Dr. Warwick, of Rotheram, contrived an apparatus which is much cheaper than the preceding one, and is shewn in fig. 2, Pl.79. A stopcock, soldered to the shorter tube in the top of the vessel, and a rim sufficiently deep to permit the water to rise an inch above the cock, will enable any one to transfer any gass with the utmost readiness to any other vessel. The stop-cock has no screw, the blow-pipe having a socket to fit the tube with sufficient accuracy to prevent the escape of air. Phil. Mag. xiii. 256.

Mr. Cavallo's is represented at fig. 3, Pl. 79 where A is a section of the vessel, made of glass or tin; B, a funnel, into which is fastened a bent glass tube, C; D, is a tube soldered to the funnel, and which with it passes through the cork a; E, represents a tube of tin, wood, or other materials, to one end of which a bladder or oiled silk bag is fastened; the other is inserted in the tube D. The ves sel A being filled with the required gass (by taking out the funnel, &c. filling the vessel with water, inverting it, and applying the tube leading from the apparatus where the gass is produced), whenever it may be necessary to transfer any quantity to a bottle, bladder, &c. an equal quantity of water is to be poured through the funnel B, which

will displace the gass, and force it through D, into E. The bent part of the tube C, by always coutaining some water, prevents the gass from escap ing through the funnel; but when the apparatus is to be set by, both the funnel and the tube D must be stopped with corks.

GASSES, their effects on sounds. Dr. Chladni, the ingenious inventor of the Euphon, engaged professor Jacquin of Vienna to make some experiments on those gasses which constitute our atmosphere, and serve to produce vocal sounds. Comparative experiments were made with atmospheric gass, oxygen, hydrogen, carbonic acid, and nitrous gass. The intensity of the sounds did not vary; but when compared with that produced by atmospheric air, the oxygen gass gave a sound half a tone lower; azotic gass, prepared by different methods, constantly gave a sound half a tone lower; hydrogen gass gave nine or eleven tones higher; carbonic acid gass one third lower; and nitrous gass very nearly a third lower. A mixture of oxygen gass and azote, in the proportions of the atmospheric air, afforded the same tone as atmospheric air; that is, it was half a tone higher than either of the component parts alone. When the two gasses were not uniformly mixed, the sound was abominably harsh. Maunofr, and Paul of Geneva, after having inspired a large quantity of pure hydrogen gass attempted to speak, but found that the sound of their voices had become shocking ly hoarse and shrill. Nicholson's Journal, vol. ii. GASSENDI (Peter), an eminent French philosopher, was born in 1592 at Charstersier, a village in Provence. Before he was 16, he was made professor of rhetoric at Digne, and soon after professor of philosophy at Aix. The celebrated Nicholas Pierese having seen his Paradoxical Exercitations, resolved to afford him leisure to pursue his studies, and in conjunction with Joseph Walter, prior of Valette, got him ordained, and procured him a benefice in the church of Digne, which he held twenty years, during which time many of his works were written. In 1645 he was appointed royal professor of mathematics at Paris. He now dedicated himself so intensely to study and astronomical observations, that his health visibly decayed. He was at first relieved by bleeding, but afterwards, when he found himself exceedingly reduced by the repetition for the ninth time of that operation, he modestly remonstrated against it. Two of three physicians that attended him yielded to his opinions but the third arrogantly insisting on the contrary opinion, Gassendi submitted, and he was bled four times afterwards. He died in 1655, in the 63d year of his age. A short time before his death he took the hand of Antony Poller, his amanuensis, and placing it on his heart, Poller observed that its motion was very faint and fluttering; Gassendi replied, "You see what is man's life;" and these were the last words he uttered. He left his manuscripts to M. de Monmor, his friend and executor.

Gassendi wrote against the metaphysical meditations of Des Cartes; and divided with that

great man the philosophers of his time, almost all of whom were either Cartesians or Gassendists. To his knowledge in philosophy and mathematics, he joined profound erudition and deep skill in the languages. He wrote, 1. Three volumes on Epicurus's philosophy; and six others, which contain his own philosophy.-2. Astronomical Works.-3. The lives of Nicholas de Pieresc, Epicurus, Copernicus, Tycho Brahe, Purbach, and Regiomontanus. Epistles, and other treatises. All his works were collected together, and printed at Lyons in 1658, in 6 volumes folio.

4.

To GAST. v. a. (from garz, Saxon.) To make aghast; to fright; to shock; to terrify; to fear; to affray (Shakspeare).

GASTEROSTEUS. Stickle-back. In zoolo gy, a genus of the class pisces, order thoracia. Head oblong, smooth; jaws armed with minute teeth; tongue short, obtuse; palate smooth: eyes moderate, hardly prominent, lateral; gill membrane with three, six, or seven rays; gill-cover of two pieces, rounded, striate, body carinate on each side, and covered with bony plates; dorsal fin single, with distinct spines between it and the head; lateral line straight; ventral fins behind the pectoral, but above the sternum. Thirteen species, scattered through the seas of Europe, Asia, and Africa. The following are the chief:

1. G. aculeatus. Three-spined stickleback. Dorsal spines three. Inhabits the fresh waters of Europe, is very short-lived, hardly ever reaching to the third year: about three inches long: spawns in April and June; is infested with internal worms; feeds on the fry and spawn of fishes, worms, and insects; appears sometimes in vast shoals, and is chiefly used for manure, or to fatten ducks and pigs.

2. G. ductor. Pilot-fish. Dorsal spines four; gill membrane, seven-rayed. Inhabits the ocean; is a constant attendant on the shark, and always precedes it.

3. G. saltatrix. Skip-jack. Dorsal spines eight, connected by a membrane; gill membrane with seven rays. Inhabits Carolina: is less spinous than others of its tribe, and resenibles a perch.

4. G. spinachia. Fifteen-spined strick leback. Dorsal spines fifteen. Inhabits the seas of Europe, and is never found in rivers: from six to seven inches long; body long, above brown or olive, beneath silvery: is said to follow a light; feeds on worms, insects, and the young fry and spawn of fishes; is seldom eaten, but used chiefly for manure or lamp-oil. See Nat. Hist. Pl. CXIX.

GASTRELL (Francis), bishop of Chester, was born in 1662, appointed preacher to the society of Lincoln's Inn in 1694, and made bishop of Chester in 1714. He preached a course of sermons for Boyle's lectures; engaged in the Trinitarian controversy with Mr. Collins and Dr. Clarke; and published two excellent pieces, the one entitled Christian Institutes, and the other, a Moral Proof of a Future State. He vindicated the rights of the university of Oxford against the archbishop of

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