264 PHILOSOPHICAL TRANSACTIONS. [aNNO 1792. 



more than a single unit in the 3d place of decimals, even in the temperature of 

 100°. The greatest difference found, in that degree of heat, was .OOO94 ; and 

 in a heat of 80°, the highest to which the tables for use were to be carried, it 

 amounted only to .OOO64 ; being in both cases greatest when the mixture con- 

 sisted of 85 parts of water, by weight, to 100 of alcohol. This difference how- 

 ever, small as it was, afforded sufficient reason for repeating all the former ex- 

 periments, conjointly with the new set for dilute spirits, so as to make one entire 

 series, with the same spirit, and executed throughout in a uniform manner. To 

 obviate the error from evaporation in this series, and ascertain what each mixture 

 really lost of its strength during the operation, all the fluids were first weighed at 

 60°, before they were cooled down to 30°; from 30° to 100°, they were weighed 

 at every 5 degrees, as before, consequently a 2d time at 60°; and lastly, after 

 having been heated to 100°, they were again brought to 6o°, and weighed at that 

 point a 3d time. The diffiirence between these weights, at the beginning, mid- 

 dle, and end of the experiment, was applied, in due proportion, to correct the 

 numbers of the respective intervals between them ; by which means it is believed 

 that the error arising from the gradual evaporation of the spirit, during the ex- 

 periment, has been made to ilisappear. Mr. Gilpin having also observed, that 

 the spirits adhering to the sides of the funnel which he employed to fill up the 

 weighing-bottle, became weak, by the evaporation, and so diluted the fresh spirit 

 poured into the funnel, determined to use a smaller instrument of this kind, 

 namely, such an one as would not hold more than 15 grains of spirit; in which a 

 less surface being left wet when the spirit ran out, the error from this cause would 

 be proportionably diminished. 



Under all these precautions were the experiments made, of which the results 

 are given in the following tables. Tliey are drawn up exactly like the tables in 

 the former report ; but, as alcohol was taken for the fixed quantity in the first 

 half, so water is taken for the fixed quantity in the last half, wliich therefore con- 

 sists of mixtures containing all 100 grains of water, with 95 grains, 90, 85, and 

 so on successively, of alcohol, till the last column is pure water. This arrange- 

 ment will be clear to every one, on reading the title of each column of the tables. 

 The first part or column of the table gives the actual weights, at the even degree 

 of the thermometer, corrected for the evaporation ; and the 2d gives the specific 

 gravities, calculated from those weights, with the same allowances and corrections 

 as were specified in the original report. 



