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Sikes's hydrometer is now generally employed, liquors leave variable proportions of water, especially since its adoption by the commis- when thus burned in a graduated vessel. sioners of his najesty's customs. This instru: There is the greatest difficulty in ascertaining ment has but nine shifting weights, applicable what is meant by the terms proof spirit. Dr. upon the upper part of the stem, and is used Thomson, quoting the act of parliament of with a set of tables, or a sliding rule sold with 1762, states, that at the temperature of 60°, the it, for computing compensation for different tem- specific gravity of proof spirit should be 0:916; peratures. The scale is divided into ten principal and he also observes, that proof spirit usually divisions, each of which is subdivided into five means a mixture of equal bulks of alcohol and parts, and by the separate application of the water; but the specific gravity of such a mixweights in succession completes the range of ture will, of course, depend upon that of the strength from pure alcohol to water, each weight standard alcohol, which is not specified. It being equivalent to ten principal divisions. This appears from Gilpin's Tables that spirit of the hydrometer, with the weight marked 60, screwed specific gravity .916, at 600, consists, by weight, on to the lower stem, is so adjusted as to sink to of 100 parts of alcohol, specific gravity •825, at the line mark P on the scale of the instrument 60°, and 75 of water; and, by measure, of 100 when placed in proof spirit, of the temperature parts of the same alcohol, and 61.87 of water. of 510 Fahrenheit, and, by the addition of the One of the most accurate and convenient mesquare weight on the top of the stem, it sinks to thods of obtaining the specific gravity of Auids the same point in distilled water of the same is by what is called a thousand grain bottle. temperature. This weight being just one-twelfth This is sold by most of the philosophical inpart of the entire weight of the whole hydro- strument makers, together with a weight, which meter, together with its bottom weight No. 60, is an exact counterpoise for the bottle when causes the scale to show the difference between filled with distilled water; its magnitude being water and proof spirit, which, the act states, adjusted by grinding down the length of its shall weigh exactly twelve-thirteenth parts of an neck, until it holds exactly 1000 grains of water equal bulk of distilled water.

at 60° of Fahrenheit. This instrument conseMr. Meikle's hydrometer consists of a glass quently requires no computation, but is simply tube, open at both ends, and bent into a kind of to be filled with fluid, and placed in one scale double syphon, having four parallel legs; so of a balance, while its counterpoise is placed that the open ends are pointed in the same direc- in the other. If the fluid put into it is lighter, tion or upwards, as shown in fig. 13, plate I. than water, it will appear deficient in weight, The manner of using it is very simple. Let one and as many grains must be added to the scale of the ends be stopped with a finger or cork, that contains it as will restore the balance. This and water be poured into the other. This Auid at once shows that the specific gravity of the will only rise a small way into the second leg, fluid under examination is negative, or less than because of the included air. Next stop the other the standard, and consequently must be a fracorifice, and open the one first closed; and, hav- tional number; but, should the fluid be heavier ing poured into the latter the liquid whose spe- than water, the bottle will preponderate, and cific gravity is to be tried, open the top of the weights 'must be put into the opposite scale, water tube; then, the instrument being held up- when their amount will be positive, and must be right, the two liquids will arrange themselves so added to the amount of the standard. For exas to press equally on the included air. This ample: if the bottle were filled with sulphuric pressure will be measured by the difference in ether, it would require 739 grains to be placed the heights of the two columns of either liquid, in the same scale to restore the balance, consemultiplied by its specific gravity, so that, by quently its specific gravity would be thus exdividing the difference of the two columns of pressed 0.739. Had it been filled with seawater by the difference of those of the other water, which is rather denser than that which is liquid, we obtain the specific gravity of the lat. distilled, twenty-six-hundredths, or rather better; that of water being unity. The difference ter than one-fourth of a grain must have been between the columns may be measured by added in the opposite scale, and these, as already applying any scale of small equal parts, or the explained, must be added to the standard 1.000 glass may be attached to a graduated plate fur- to express the specific gravity of such water, nished with verniers, &c. The longer the which would be thus written 1.026. Sulphuric columps of liquids employed, the more accurate acid again, being still heavier, would, in like the process. The expansion of the glass, or its manner require 875 grains, and would accordcapillary action, cannot affect the result, nor is ingly be expresscd 1875. it influenced by the expansion of the scale; the A bottle, however, holding 1000 grains is often only correction required will be to reduce the inconveniently large, and a small and thin globobservations to one temperature.

ular phial, with a piece of thermometer tube There are other methods of judging of the ground into it by way of stopper, will be found strength of spirituous liquors, which though more useful · such a phial should not weigh useful are not accurate, such as the taste, the more than from fifty to sixty grains, and may size and appearance of the bubbles when shaken, contain between 400 and 500 grains of water. the sinking or floating of olive oil in it, and the To use it it should be accurately counterbalanced appearances that it exhibits when burned ; if it in a delicate pair of scales, and then filled with burns away perfectly to dryness, and inflames distilled water, and the stopper thrust in, the gunpowder, or a piece of cotton immersed in it, capillary opening in which allows a little to ooze it is considered as alcohol; the different spirituous qui, and prevents the likelihood of bursting the

phial; it is then to be wiped clean and dry, and The following table is given by Mr. Gilpin, again carefully weighed, by which the quantity in the eighty-fourth volume of the Philosophical of water it contains is ascertained; the water Transactions, and is of essential use for taking being poured out it is next filled with the liquid the specific gravities both of solids and fluids, whose specific gravity is required, taking care by enabling the operator to reduce the weight or that it is of the same temperature as the water; bulk of the distilled water, employed in any we then weigh as before, and divide the weight case, to that which it would have at any other by the foriner weight of water, the product gives common temperature, and particularly to 60°, the specific gravity required. Thus, suppose which is the usual standard. the phial to contain 425 grains of water at the Thus, for example, since the specific gravity temperature of 450, it will be found to hold of water at 47° is 1.0008 grains, and at 60° is 5737-5 grains of pure mercury of the same tem- 1.00000, (and consequently 1.0008 grains, at 47°, perature; and 5737-5 • 425 = 13.5 the speci- are equal in bulk to 1:00000 grains at 600), it fic gravity of mercury. Or, supposing the follows that it would require 252.708 grains at liquid lighter than water, such as alcohol, of 47°, to equal the space of a cubic inch; for which we may assume the pnial to contain 350:5; 1:00000 : 1.0008 :: 252.506 (the weight of a then 350:5 · 125 = 0·824, the specific gravity cubic inch at 60°), : 252.708. of the alcohol under trial.

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Table of the Specific Gravity of Water, at every Degree of Temperature, from 30° to

80° Fahrenheit.
Fabr.
Specific Gravity.
Fahr.

Specific Gravity.
1.00074
56°

1'00031 31 1.00078

1.00024 32 1.00082

1:00016
1 00085

1.00008
34
1.00088

1.00000
1.00090

0.99991 1.00092

0.90981 37

1.00093
63

0.99971 38

1.00091
64

0-99961
1.00094
6.5

0.99950
1.00091

0-99939 1.00093

0.99928 42 1.00092

0.99917 43

1.00090
69

0-99906
1'00088

0.99894 45 1.00086

0.99882 46 1:00083

0.99869 47 1.00080

0.99856 1:00076

0.99843 1.00072

0-99830
1.00068

0.99816
1'00063
77

0.99802
1.00057
78

0.99788
1.00051
79

0.90774 54

1.00015
80

0.99759 55

1.00038

66 67

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The above particulars are essential to a right cerned; but we must not close this view of hyunderstanding of our subject, as far as water, drostatic equilibrium without furnishing a more which is the standard of comparison, is con- general table.

Table of SPECIFIC GRAVITIES.
Acid, Acetic . . 1.062 Do. solid . 2•800, Barytes, sulphate of, from
Arsenic . . 3.391 Sulphuric . , 1.850

4.000 to 4.865 Arsenious. . 3.728 Agate . . . . 2.590 Do. carbonate of, from Benzoic . . 0.667 Alcohol, absolute . . 0.797

4.100 to 4.600 Boracic, crystallised 1:479 Do. highly rectified 0.809 Basaltes. from 2-421 to 3.000

Do. fused : 1.803 Do. of commerce. 0·835 Beryl, oriental . . 3.549
Citric

. 1.031 Alum . . . . 1.714 Do, occidental. . 2:723 Formic . . 1'116 Amber. from 1.065 to 1.100 Blood, human . . 1.053 Fluoric . . 1.060 Ambergris from 0-780 to 0.926 Do. crassamentum of 1.245 Molybdic . 3.460 Amethyst, common , 2.750 Do. serum of . . 1.030 Muriatic . . 1.200

oriental , 3:391 Borax . . . 1714 Nitric . . 1.271 Amianthus from 1.000 to 2.313 Butter

0.942 Do. highly concen Ammonia, aqueous 0-875 Camphor .

0.988 trated . . 1.583 Arragonite . . . 2.900 Caoutchouc, or Indian Phosphoric, liquid 1.558 Azure-stone ; : 2.850 rubber

· 0933

Table of Specific GRAVITIES.—Continuea Cornelian, speckled . 2.6131 Sulphureted do. 1.180

or not. , 7788 Chalcedony, common, from

Sulphurous acid 2.222 Lead . . 11:38 2.600 to 2.65 Glass, crown . . 2.520 Manganese

8.000 Chalk. from 2.252 to 2.657 green . . 2.642 Mercury, solid, 30 Chrysolite 3400 Aint from 2.760 to 3.000

below 0 of Fahr. 15.61 Chrystalline lens of the eye 1.100 plate . 2.942 Do. at 32° of Fahr. 13.61 Cinnabar, from Almaden 6.902 Granite from 2.613 to 2.956 Do. at 60° of Fahr. 13:58 Coals from 1.020 to 1.300 Gum arabic . . . 1.452 Do.at 212° of Fahr. 1337 Copal . . . 1.045 cherry-tree . . 1.481 Molybdenum 8.600 Coral, red, from 2.630 to 2.857 Gunpowder, loose . 0·836 Nickel, cast . 8.279 white, from 2-540 to 2.570

shaken : 0.932

forged , 3.666 Corundum . . . 3-710

solid . . 1.745 Osmium and RhodiCyder. : ... 1.018 Gypsum, compact, from

um, alloy of. 19.50 Diamond, oriental, color

1.872 to 2.288 Palladium

11.80 less . . 3.521 crystallised, from

Platinum . ; 21:47 Do. colored varieties, from

2.311 to 3.000 Potassium at 59° 3.523 to 3.550 Heliotrope, or bloodstone

Fahr. . , 0.865 Do. Brasilian . . 3.444 from 2.629 to 2.700 Rhodium

10-65 Do. colored varieties, from Honey . . . . 1.450 Selenium

4.300 3.518 to 3.550 Honeystone, or mellite, from

10.47 Dolomite from 2-540 to 2.830

1:560 to 1.666|

hammered 10-51 Dragon's blood (a resin) 1.204 Hornblende, common, from

Sodium at 59° Fahr. 0.972 Ether, Acetic . 0866

3.250 to 3.830 Steel, soft . 7833 Muriatic . . 0°729

basaltic, from

tempered 7.816 Nitric i 0.908

3:160 to 3.333 Steel, hardened 7.840 Sulphuric. from Hornstone from 2-533 to 2.810

tempered and 0632 to 0-775 Hyacinth from 4.000 to 4.780

hardened 7.818 Emerald from 2.600 to 2:770 Jasper : from 2358 to 2.816 Tellurium, from Euclase from 2.900 to 3.300 Jet . . . . 1.300)

5.700 to 6.115 Fat of Beef . . .0.923 Indigo .

. 1.009 Tin, Cornish . 7.291 Hogs . . 0.936 Ironstone from Carron. 3.281 Do. hardened 7.299 Mutton . . 0.923, Do. Lancashire 3.573 Tungsten

1740 Veal

· 0-934 Isinglass . . . 1•111 Uranium . . 9.000 Felspar from 2:438 to 2.700 Ivory . . . . 1.825 Zinc from 6.900 to 7.191 Flint, black . . 2.582 Lapis Nephriticus. . 2.894 Mica from 2.650 to 2.934 Gamboge. . 1.222 Lard . . . . 0.947 Milk .

. 1.032 Garnet, precious, from

Lead, glance or galena from Mineral pitch, or asphal4.000 to 4.230 Derbyshire, from 6-565

tum, from 0.905 to 1.650 Do.common, from 3.576 to 3.700

to 7.786 Mineral tallow . : 0.770 Gases, Atmospheric air 1.000 Limestone, compact, from Myrrh (a resin) . . 1.360 Ammoniacal . 0590

2.386 to 3.000 Naphtha from 0.700 to 0-847 Carbonic acid, 1.527 Magnesia, native, hydrate Nitre . . . . 1.900 Carbonic oxide 0.972 of . . . : 2.330 Obsidianum from 2-348 to 2.370 Carbureted hydro

Do. carbonate of, Oils, Essential-Amber 0.868 gen . . 0:972 .

from 2.220 to 2.612

Anise-seed 0.986 Chlorine, . 2.500 Malachite, compact, from

Carraway-seed 0.904 Chlorocarbonous

3.572 to 3.994

Cinnamon 1.043 acid . . 3.472 Marble, Carrara. . 2.716

Cloves

. 1.036 Chloroprussic acid 2.152 white, Italian : 2.707

Fennel . 0.929 Cyanogen. 1.805 black veined 2704

Lavender 0.894 Euchlorine . 2.440 Parian , 2560

Mint, common 0.898 Fluoboric acid. 2-371 Mastick (a resin). 1.074

Turpentine 0.870 Fluosilicic acid 3.632 Melanite, or black garnet,

Wormwood 0.907 Hydriodic acid 4.340

from 3.691 to 3.800 Expressed—Sweet alHydrogen . .0.069 Metals, Antimony . 6702 monds . 0.932 Muriatic acid . 1.284 Arsenic .5763

Codfish . 0.923
Nitric oxide 1.041
Bismuth . . 9.880

Filberts - 0.916
Nitrogen . 0972 Brass, from 7-824 to 8.396

Hempseed 0.926 Nitrous acid 2.638 Cadmium. . 8.600

Linseed . 0.940 Nitrous oxide 1.527 Chromium . 5.900

Olives . 0.915
Oxygen . 1'111 Cobalt . 8.600

Poppyseed 0.939
Phosphureted hy-
Columbium 5.600

Rapeseed 0-913 drogen . 0.902 Copper . . 8.900

Walnuts from
Prussic acid 0.937 Gold, cast. 19.25

0-923 to 0.947
Sub-carbureted hy-
Do. hammered. 19.35

Whale - 0.923 drogen. 0.555 Iridium, hammered 23.09 Opal, precious . . 2.114 Sub-phosphureted

Iron, cast at Carron 7-248 Do.common, from 1.958 to 2.114 ditto . : 0.972 Do. bar-hardened, Opium . .

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· 1028

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Table of SPECIFIC Gravliles. - Continued. Orpiment from 3.048 10 3:5001 Do. carbonate ot,

Cedar, Indian 1.315 Oyster-shell . 2 092

from 3.658 to 3.075

American 0.561 Pearl, oriental, from 2.510 Stone, Bristol, from 2.510

Cherry-tree 0.715 10 2:750

to 2610
Citron

0.726 Pearlstone . . 2.340 cutlers' . . 2.111 Cocoa-wood 1:010 Peat

from 0:000 to 1:329 grinding . 2.142 Crab-tree : 0705 Peruvian bark . : 0.7841 hard . . 2.400 Cork

: 0240 Phosphorus . . 1.770 paving, from 2:415

Cypress, Spanish ( 644 Pitchstone from 1.970 to 2.7.20

to 2:708 Ebony, American 1.331 Plumbago, or graphite,

Portland . . 2:490 Do. Indian 1.209 from 1.987 to 2:4001 Rotten

Elder-tree : 0.695 Porcelain from China 2:384 Sugar

1.606

Elm-tree . . 0.071 Sèvres 2 145 Sulphur, native . 2.033

Filbert-tree

0.600 Porphyry from 2:452 to 2.972 f used . 1.990

Fir, male

0:350 Porphyry, Seltzer . 1.003 Tale . from 2.080 to 3.0001 Do, female

0:198 Proof-spirit . 09:23 Tallow . . , 0041

llazel

(-600 Pumice-stone from 0.752 10 ():914/Topaz from 4:010 10 4.0011 Jasmin, Spanish 0:770 Quartz from 2.624 to 3.750 Tourmaline from 3.086 10 3:362 Juniper-iree : 0:556 Realgar from 3.225 to 3 338 Turquoise, from 2:500 10 3.000 Limon-tree . 0.703 Rock-crystal from 2:581 to 2.888 l'ltramarine . . 2.300 Lignum vitæ 1:333 Ruby, oriental . . 4.283 Cranite . . . 2190' Linden-tree

0.004 Sal gem . . . 2.145 Vesuvian from 3.300 to 3:5751 Mastick-tree 0.849 Sapphire, oriental, from Vinegar from 1:013 to 1.030

Wahovany

1.003 4.000 to 4.200 Water, distilled . . 1.000 Maple-tree : 0.750 Sardonyx from 2002 to 2.628 sea

Vidar

0944 Scammony of Smyrna 1.274 Water, of Dead Sea 1.240 Mulberry, Spanish 0.897 Aleppo 1 235 Wax, bees'

0904 (ak-heart, 60 yrs. Schorl from 2-922 to 3:452 white

0968

old . . 1.170 Serpentine from 2.204 to 2.999 sboemakers' . 0:897| Olive-tree - 0.927 Shale . . . . 2.600 Whey, cows'

. 1.019, Orange-tree - 0.705 Silver glance, from 5:300 to 7.208/1line, Bourdeaux

Pear-tree

0:160 Slate (drawing) . . 2.110 Burgundy . 0.991 Pluin-tree . (.785 Smalt . . 2:4101 Constance

• 1.081

Pomegranate-trer 1.301 Spar, fluor, from 3:094 to 3.791 Malaga

1.022 Poplar-tree : 0:383 Do, calcareous, from 2:020

Port :

0.007 Do, White Spanish 0:529 10 2.837 Ibite Champagne 0.997 Quince-tree : 0.705 Do. double refry. from Wood, Alder

0.800

Sassafras . 0:482
Castleton : 2:7:24 Apple-tree

0.793
lie

1.327 Spermaceti . : 0.943 Ash

0.815 Walnut

0.081 Spodumene or triphane, Bay-tree . 08:22 Willow

(185 from 3.000 to 3.218 Beech

08.52, Yew, Dutch : 0.788 Stalactite from 2-323 to 2.540 Box, French . 0:912 Spanish

. 0-807 Steam of water . . 0:481

Dutch : 1.328' Knot of 16 yrs. old 1.760 Steatise from 2:400 10 2.665 Brasilian, Red 1:031, Woodstone from 2:04.5 to 7.075 Stilbite from 2:110 to 2:300 Campeachy . 0.913 Zeolite from 2.073 10 2718 Strontian, sulphate of, from

Cedar, wild : 0:596'Zircon from 7:385 to 1.700* 3.583 to 3.958

Palest 0:013 * It may be proper 10 add, that Mr. S. L. Keni, to whom we are indehted for much valuable informu1011 on this subject, has nearly completed the most extensive and accurate series of observations on the specitic gravity of mineral bodies that has ever been attempted.

Hlavios in the preceding portion of our follow, it will continue to flow out of the vessel, article examined the nature of hydrostatic through the tube B (, as long as the aperture A pressure, we may now proceed to treat of fluids is under the surface of the liquor. Or if the in motion, and the structure of hydraulic ma- syphon be at first filled with the fluid, and the chines.

aperture ( stopped with the tiger until the One of the most simple instruments for rais. aperture A is immersed, the event will be premg water is the syphon; a bent tube which cisely the same. During the process of sucking, owes its operation to the pressure of the atmo- the air in the tube is rarefied, and the equilibrium sphere. The ordinary syphon is represented at destroyed; consequently the water must be fig. 1, plate II., HYDROSTATICs and Hydral- raised into the less leg AB, by the preponderlics; and consists of a crooked tube ABC', ating pressure of the atmosphere. The syphon of such a length, and with such an angle, or so being thus filled, the atmosphere presses equally bent at the vertex, as that, when the orifice A is on each extremity, so as to sustain any equal placed on a horizontal plane, the height of AB quantity of water in each leg; but the air not may not exceed thirty-two or thirty-three fret. being able to sustain all the water in the longer Jior common uses a foot or half a foot high lep, and being more than able to sustain that in suffices. If now the less arm AB be immersed the shorter leg, with the excess of force, therein water, or any other liquid, and the air be fore, it will raise new water into the shorier sucked out of it buite aperture ( till the liquor loss; and this new water cannot rahe 11s way but by protruding the first before it : by this instrument is dependent on the discharging ley means the water is continually driven out at the being the longer of two, the greater the differJouger leg, as fast as it is raised by the ence in favor of this leg, the greater will be the shorter.

force employed in promoting the discharge. The syphon will raise a stream of water to a The improved syphon of M. Buten is shown considerable altitude in every situation where a at fig. 3, where A B is the long branch, with a little descent can be procured, but, while the bulb at A, and DC the short branch. This operation continues, no water can directly be syphon requires neither to be blown into, nor taken out of the stream above the lowest part of any suction. It is sufficient to fill the long the tube. When, however, the two open ends branch A B, and the ball A with the liquid, and of a syphon are closed, a quantity of water may to plunge che short branch C D into the liquid be let out of the highest part, and its place to be decanted. The bulb A, in emptying itself, supplied by introducing a like quantity of no draws off the liquid in contact with the short use all the avenues for the purpose being then branch, and, though the bulb itself is partly closed, and the stream suffered to flow through empty, the flow is unremitting. the tube, the useless water will be displaced, and Another improved syphon by M. Hempel, is a fresh quantity may be soon after drawn off. shown at fig. It has the same advantages as This mode of exchanging Auids may be useful that of M. Buten, and is more easily constructed in furnishing a supply for domestic purposes; on a large scale. A part of the liquid to be but there are some cases in which the water decanted is poured into the funnel A, at the top drawn off by this arrangement would not be of the tube A B, which is fitted into the shoit thought sufficiently pure. To effect the same branch of the syphon. As soon as the flow end the following apparatus has been suggested. commences, through the long branch D C, the In the upper part of the syphon E E, fig. 2, tube A B is withdrawn, and the flow of water plate II., are inserted two small pipes, and their continues. apertures in the inside of the tube should be The syphon is also occasionally disguised to divided by a projecting piece a quarter of an form a philosophical toy, called Tantalus's cup, inch thick; wherever the pipes are inserted, the from the well known fable. This c'p has a piece must be placed in such a position that the hollow stem, as at y, fig. 5, into which a small current will strike against one of its flat sides. glass syphon z is cemented in such a manner The pipe which opens on that side of the ob- that the upper bend of the syphon may be a stacle, or dam, struck by the stream, may be little below the top of the cup, and the shortest called the water-pipe, and that on the other leg a may very nearly touch it. On pouring side the air-pipe. 'nsert their other ends into a water into the cup it will rise to its proper level circular vessel, the air-pipe opposite to c must in the tube a, but still the cup will hold water, rise to near the top of this vessel, but the water- but, on attempting to fill it, the water will still pipe o need not rise above the place of its inser- rise up the tube a until it reaches the bend, tion; a cock perfectly air-tight must be fixed in which it will flow over and thus fill the whole each pipe between the vessel and syphon ; the of the longer leg z b, and the instant this is vessel must also have a tube in its lower part effected the water will flow continuously from b for letting out water. This tube must have a until the cup is quite emptied. The upper part cock fixed in it, or a valve, covered with leather, of the syphon za may be concealed by placing to close its lower end. To hasten the delivery a hollow image of a man over it, with the chin on of the water in this vessel, the external air may a level with the bend of the syphon, when the be admitted in such a inanner as is most con- cup will hold water until filled to the chin of the venient.

figure, but the water will begin to flow away as The communication between the vessel and soon as it reaches that point. syphon being intercepted by turning the cocks The strange appearance of intermitting springs, in the pipes c o, and the branches closed at their or springs which run for a time and then stop lower ends, the tube may be filled with water altogether, and after a time run again, and then through an aperture in the top. After this aper- stop, is entirely occasioned by the channels in ture is closed, and a stream of water let into the which the water flows being formed like syphons. cistern o for supplying the syphon, the ends of Thus if A B C fig. 6, plate II., represents a hill the branches may be opened, and a continued or mountain, in which there is a hollow E F G, stream will flow through the tube.

and a channel bent like a syphon F H B leading When it is required to fill the vessel c o with out of it. The water collected from the rills d water, exclude the external air, and open the will fill the hollow, and, as soon as it rises to pipes between it and the sypbon. The vessel the line 0 P, of the same height with H, it will will soon be filled, and the water may be let out rise to H in the channel, and then flow out by opening the tube for that purpose ; after which through B, till the whole runs off to the level of the small pipes are again closed by turning F. It will then cease to flow until the hollow is the cocks.

again filled to the level O P, when it will flow In estimating the discharge by a syphon, the again, and so on. Some springs called variable head of water must be reckoned equal to the or reciprocating, do not cease to flow, but only difference between the levels of the surface of discharge a much smaller quantity of water for he water, and of the lower orifice. The reason a certain time, and then give out a greater of this will be obvious, when it is recollected quantity. This is owing to the hollow being that the length of the shorter leg is only mea- supplied from another hollow, which is situated sured to the surface of the water, however far it higher up, and has a common runner going to way reach below; and that, as the action of the join the stream below the bend ll; for this

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