442 



HYDRODYNAMICS, 



Hytlrome- In this manner Mr Hutton has calculated a series of 

 te " 1 tables for giving the quantity of spirits by inspection. 

 ""Y"^ At the top, in the centre, is the specific gravity of the 

 spirits, commencing at 916, and ending with 934, and 

 embracing the different specific gravities at which spi- 

 rits are usually met with in commerce. On the right 

 of the number denoting the specific gravity, and on the 

 same line with it, is the approximate weight of one gal- 

 lon of spirits of that specific gravity, expressed in 

 pounds and ounces. The tables consist of two sets of 

 columns ; one contains the number of gallons, and the 

 other their weight: they begin with SOgallons, being the 

 smallest quantity it is considered necessary to weigh, 

 and increasing by single gallons, they extend to 185 

 gallons, being the contents of the largest cask used in 

 trade. 



122 with spirit, whose specific gravity was 928. As 

 this instrument was too large, I was obliged to incline 

 it, in order to prevent the fluid from issuing in a con- 

 tinued stream. In the first experiment, N=724, =r 

 2117, Srrl.OOO, 4=920. Hence if rf=1500, we have 



I)r Brews- 



ter's capil- 

 lary hydro- 

 " meter. 



PLATE 

 CCCXIV. 

 Fig. 6. 



18. Dr Bretvsler's Capillary Hydrometer. 



This instrument is founded upon a principle which 

 was never before employed in hydrometrical measure- 

 ments. It is well known that alcohol is a much more 

 perfect fluid than water, possessing much less viscidity, 

 in consequence of the small force of cohesion which ex- 

 ists between its particles. Hence it follows, that if a 

 vessel containing alcohol is emptied through a capillary 

 tube, so as to discharge the fluid only by drops, the 

 drops will be much smaller, and consequently much 

 more numerous, than when the same vessel is filled 

 with water and emptied through the same tube. The 

 capillary hydrometer, which is founded on this princi- 

 ple, is represented in Fig. 6. where ABC is a glass ves- 

 sel three, or four, or five inches long, having a hollow 

 bulb B about half an inch or an inch in diameter. This 

 instrument is filled by suction at the lower end C, and 

 the water is discharged at C till it stands nearly at the 

 point m, the zero of the scale. By removing the finger 

 from the lower end C, the water is discharged by drops, 

 and the number of drops which fall till the fluid de- 

 scends to another fixed point n are accurately counted. 

 This experiment is carefully repeated at different tem- 

 peratures, so that the number of drops of distilled wa- 

 ter contained in the vessel between the points m and n 

 is known for various temperatures. Hence, if N is 

 the number of drops of water whose specific gravity is 

 S, and n the number of drops of alcohol whose specific 

 gravity is s, and d the number of drops given by any 

 other mixture of alcohol and water, then n N : S s= 



(J_N)(S *) (rf_N)(S s) 

 d N:- '- -.andthereforeS i -^= 



n N n N 



will be the specific gravity of the mixture required. 

 The same experiment is made with the purest alcohol, 

 and the number of drops carefully marked. With an 

 instrument of this kind, the number of drops necessary 

 to empty it when filled with water was 724, whereas 

 when it was filled with' ordinary proof spirits, the num- 

 ber of drops amounted to 2 1 1 1. This experiment, which 

 was performed rudely, for the purpose of obtaining a 

 general idea of the magnitude of the scale, was made 

 nearly at a temperature of 60. Now as the specific 

 gravity of the spirit was about .920, and that of water 

 1.000, we have in the present case no less than a scale 

 of 1393 drops for measuring specific gravities between 

 .920 and 1.000; that is, a variation in the fifth figure, 

 or in the fourth place of decimals of the specific gravity, 

 nearly corresponds with a variation of two drops. 

 With another instrument made on a very small scale, 

 the number of drops amounted to 47 with water and 



Hydrorae. 



tcrs. 



S 



(S s) _ 1.000776 X 0.080 

 N 1393 



= .9555. 



The bulk of a drop of water will be about 2.93 times 

 as large as the bulk of a drop of the spirit used in the 

 first experiment. Inthe2d experiment, the drop of wa- 

 ter was 2.6 times greater than the drop of the spirit. 

 See Chapter V. p. 473 of this article. 



19. Sikes' Hydrometer. 



As this hydrometer is now universally used in the Sikes' hy. 

 collection of the revenue in both kingdoms, we shall drometer. 

 lay before our readers a drawing and description of it, 

 although it does not differ much in principle from the 

 ordinary hydrometers. It is represented in Plate PLATE 

 CCCXIV. Fig. 7. where AB is a flat stem 3.4 inches CCCXIV. 

 long, which is divided on both sides into 11 equal >8 ' ' 

 parts, each of which is subdivided into 2, the scale being 

 numbered from to 11. This stem is soldered into a 

 brass ball 1.6 inch in diameter, into which is fixed a 

 small conical stem CD, 1.13 inch long, at the end of 

 which is a pear-shaped loaded bulb DE, half an inch in 

 diameter. The whole instrument, which is made of 

 brass, is 6.7 inches long. The instrument is accompa- 

 nied with 8 circular weights, numbered 10, 20, 30, 40, 

 60, 60, 70, 80, and another weight of the form of a pa- 

 rallelopiped. Each of the circular. weights are cut in 

 to their centre, so that they can be placed on the coni- 

 cal stem C, and slide down to D ; but in consequence 

 of the enlargement of the cone they cannot slip off at D, 

 but must be brought up to C for this purpose. The square 

 weight, of the form of a parallelepiped, has a square notch 

 in one of its sides, by which it can be placed upon the 

 summit A of the stem. In using this instrument, it is 

 immersed in the spirit, and pressed down by the hand 

 to 0, till the whole divided part of the stem be wet. 

 The force of the hand required to sink it will be a guide 

 in selecting the proper weight. Having taken one of 

 the circular weights which is necessary for this purpose, 

 it is slipped on the conical stem at C. The instrument 

 is again immersed and pressed down as before to 0, 

 and is then allowed to rise and settle at any point of the 

 scale. The eye is then brought to the level of the sur- 

 face of the spirit, and the part of the stem cut by the 

 surface, as seen from below, is marked. The number 

 thus indicated by the stem is added to the number of 

 the weight employed, and with this sum at the side, 

 and the temperature of the spirits at the top, the 

 strength per cent, is found in a Table of six quarto pa- 

 ges. " The strength is expressed in numbers denoting 

 the excess or deficiency per cent, of proof spirit in any 

 sample ; and the number itself (having its decimal point 

 removed two places to the left) becomes a factor where- 

 by the gauged content of a cask or vessel of such spirit 

 being multiplied, and the product being added to the 

 gauged content if overproof, or deducted from it if un- 

 der proof, the result will be the actual quantity of 

 proof spirit contained in such cask or vessel." 



The instrument is also accompanied with three slid- 

 ing rules made of boxwood, which may be used instead 

 of the Table. ' The officers of excise are directed to 

 estimate the temperature by the nearest degree above 





