VOL. LXXXIII.] PHILOSOPHICAL TRANSACTIONS. 317 



except vitriolic aether, and not even by that, except when particularly prepared 

 for the purpose. The cavity left at the upper part of the stopper may be filled 

 up with sealing-wax, or any other kind of cement; this will assist in fixing the 

 tube, and as the liquors to be weighed do not come in contact with this part, if 

 the bottle be carefully filled, there is no danger that the wax, or cement made 

 use of, should in any degree affect the accuracy of the experiments. 



The manner of using this instrument, and preparing it for experiments, is 

 as follows. (1.) A. An accurate cubic inch, which is fastened, by means of a 

 horse-hair, to a hydrostatic balance, is to be suspended in a vessel with distilled 

 water, of the temperature of 60° of Fahrenheit; when the sum of the weight 

 which the cubic inch thus loses, in the water, will be equal to the weight of an 

 equal quantity of water displaced by it. (2.) b. The instrument, free from 

 moisture, is then to be put into the scale of an accurate balance, and its weight 

 ascertained, from which the weight of the common air contained in the bottle 

 must be deducted; when the remainder will indicate the absolute weight of the 

 instrument. (3.) c. The bottle of the apparatus is then to be filled with dis- 

 tilled water, of the temperature of 6o°, and the stopper, with the thermometer, 

 fitted to the bottle, so that neither the smallest bubble of air may remain in it, 

 nor anv of the fluid adhere to the outside of the stopper or bottle; after which 

 the weight of the water is to be ascertained, and marked on the bottle, from 

 which, by calculation according to experiment A, the quantity of water, con- 

 tained in the bottle in cubic inches measure, may be found. Having thus as- 

 certained the quantity of water of 6o° of temperature which the bottle contains, 

 the bottle may then be filled with any other fluid of the same temperature, and 

 its weight ascertained, according to experiment c, and compared with that of 

 distilled water. If, for example, the bottle be found to contain 327 grains of 

 distilled water, and 654 of another fluid, the difference will be as 1 to 2; or 

 654 divided by 327, will give 2 for the quotient. The specific gravity then of 

 the fluid thus found, compared with that of distilled water, is properly expressed 

 by the ratio 2.000 to 1.000; which latter expression is taken for the standard. 



As it is a known fact that fluids exhibit different specific gravities at different 

 temperatures, it would have been necessary to form a table, exhibiting the spe- 

 cific gravities of fluids at different temperatures, had Mr. S. not, in order to 

 avoid this inconvenience, hit upon a method of bringing the fluids, whose specific 

 gravities are to be investigated, to a certain standard, viz. to 6o°, by setcing the 

 bottle with the fluid in a glass vessel with cold water, and adding as much warm 

 water as may be necessary to bring that fluid to this standard of 6o°. As the 

 fluor acid will in some measure dissolve the glass, it becomes necessary, when 

 that acid is to be weighed, to coat the inside of the bottle, by melting a little 

 bees-wax in the bottle, and turning it, with the thermometer, in such a manner 



