HYDRODYNAMICS. 



441 



it- specific gravities f solid*, does not differ very essential- 

 ly from the hydrometer of Nicholson. It has a contri- 

 W ~V"*' vance, however, for inverting % Uie lower basin, when 

 the solid whose specific gravity is required is lighter 

 than water. In this case the basin is inverted, and the 

 solid presses upwards against its bottom, and tends to 

 elevate the hydrometer. See Blot's Trails de Physique, 

 torn. i. p. 433. 



16. Dr Wilton's Hydrometer irith Gltut Beadt. 



Dr wj. The late Dr Wilson, professor of astronomy in the 

 oo' hydro- university of Glasgow, proposed to measure the speci- 

 1 fie gravities of fluids by a series of small glass beads, or 

 hollow balli, differing from each other in specific gravi- 

 ty. When any of the beads are thrown into the fluid, 

 all those that are heavier than the fluid sink to the bot- 

 tom, while those that are lighter float upon the surface. 

 By holding the vessel either in the warm hand, or near 

 a fire or candle, the fluid will dilate, and one of the 

 glass beads will sink. Hence it follows, that the specific 

 gravity of this bead, which is marked upon it, was ci- 

 ther equal to, or a little less than that of the fluid before 

 the beat was applied. If any of the beads should hap- 

 pen to be broken, the specific gravity of the liquor may 

 be determined by the other beads; for the liquor in 

 which No. 4. sinks will also allow No. 2. to sink )>y 

 beating it a few degrees, so that No. 3. may be dispen- 

 sed with. Complete sets of these bubble*, with a small 

 treatise pointing out the method of using them, were 

 made by Mr Brown, an artist in Glasgow, and have 

 been pretty generally used by spirit-dealers. In some 

 of thcx seta, the numbers upon each br id are the num- 

 ber of gallons of proof spirits contained in 100 gallons 

 of the liquor ; while in odier set*, the number expresses 

 the gallons of water which will make a liquor of that 

 strength, if added to 14 gallons of alcohol 



I m ', pi. 



[fO - " >- 



mm. ^ 



17. T*rft Pale* Artomeirical Beodt. 



The patent areometrical beads have been brought to 

 a very high degree of perfection l-y Nfrs Lovi. They 

 an now used by many of the fim ilirtillen and practi- 

 cal chemists, and have been honoured with the hifhiat 

 approbation of some of the principal philosophers and 

 chemists in Scotland. The patent beads are fitted up in 

 boxes, containing diderent quantities, according to the 

 purposes fix- which they arc wanted, and they are al- 

 ways numbered to every two unit* in the 3d place of 

 specific gravity ; for example, 920, 9W, 0*4, &c . if 

 thev are required merely for >pirituou* liquors, thir- 

 ty beads will be sufficient ; but if they are required 

 for all fluids, from ether to the most concentrated 

 sulphuric acid, thru- hundred at least will be requi- 

 red. As these beads are marked with their respec- 

 tive specific gravitiea, we have only to throw a par- 

 cel of them into the fluid till we find the one that stands 

 in the middle of the liquid without eitlier rising to the 

 top or sinking to the bottom. The number marked 

 upon this bead will indicate the specific gravity of the 

 fluid. The beads are accompanied by a sliding rule 

 and a thermometer for nuking the corrections for diffe- 

 rences of temperature, and for finding the strength of 

 the spirits, in the language of spirit dealers and excise- 

 officers. The supt ; -.uis hydrometer to every 



other instrument with which we are acquainted, is very 

 great If the or;l;:ury fi> (lr>,ineUr meets with any ac- 

 . it is incapable of being repaired; but if any of 

 xi. i AKI u. 



the areometrical beads are broken, they can easily here- Hydrowo- 

 placed, and the specific gravity may be determined with ^ 

 sufficient accuracy, it' one or even two beads of the se- """V 

 ries are destroyed. 



The areometrical beads have been applied with great 

 success by Mr Hutton to an improved method of ascer- 

 taining the quantity of spirituous liquors by weighing 

 instead of measuring tht-tn. 



" The weight of a very large quantity," says Mr Hut- 

 ton, " may be ascertained at one operation, in a short 

 time, and comparatively with little trouble. Now, if the 

 weight of a cask be ascertained when empty, and after- 

 wards when filled with spirits, the difference of these 

 weight* will be the weight of the spirits the cask con- 

 tains ; and since the specific gravity of spirits is easily 

 found by mean* of the patent beads, we can thus obtain 

 with the greatest facility both the weight and specific 

 gravity of the spirits ; and from these data, it is eay to 

 calculate the quantity which a cask may contain, in 

 terms of any given measure. 



C. Qr. llxoi. 



Thus, suppose that a cask weighs, when! j 3 2 a 

 empty ...... J 



And when filled with spirits, . . 12 9 



The difference or weight of the spirits? 

 will be ...... J 





And suppose that the spirit is of the specific gravity 

 980, and that it is required to find the number of wine 

 gallons which the cask contains, 



We may proceed in this manner : 



Sine* a cubic foot, or 1728 cubic inches, of spirit of 

 this strength weighs 98O ounces, and a wine gallon 

 contains <M1 cubic inches ; to ascertain the weight of a 

 wine gallon of such spirits we have this proportion : 



In. Os. In. Ok, 



1728: 920 : : SSI : - - the weight of a wine 



1 IXO 



gallon of spirits of the specific gravity 920. 



And to ascertain the number of wine gallons or quan- 

 tities of the weight .-^^ - ounces, contained in 



IOC. 3qrs. 25 Ib. 14 ox. or 19,678 ounces, we have 

 this proportion : 



O. Qttt. 



Of. 



*-?!, 1,19,678: 



Gilt. 



19.67R 



< 19678 



= 160. 



A quantity of spirits, therefore, of the specific gra- 

 vity 990, and which weighs IOC. 3qrs. 25 Ib. 14o. 

 will measure exactly lf>0 wine gallons. 



It i< easy also, the number of wine gallons and spe- 

 cific gravity being given, to calculate the weight. 

 Thm, in the above example, all the alteration that tins 

 state of the question would have occasioned, would 

 have been in the second proportion, which would have 

 stood thus: 



Call. Os. 



Gall. 



Oi. 



C. Qr. IK or. 



: X X.Xl- 10* 251* 



ITS 

 IK 



