on Spirituous Liquors* 325 
that degree of irregularity in the firft differences as made it ad- 
vifable to repeat ieveral of the experiments ; and Dr. Doll- 
fuss leaving England about that time, the bufinefs of this re- 
petition was intruded to Mr. Gilpin, Clerk of the Royal So- 
ciety. This gentleman had already taken a part in the bufinefs, 
by affifting Dr. Dollfuss in the former experiments, parti- 
cularly in the very nice part of weighing the mixtures ; and 
his great (kill, accuracy, and patience, in conducing experi- 
ments, as well as in computations, had on other occasions been 
proved to many Members of the Society. One experiment 
leading on to another, Mr. Gilpin was at length induced to go 
through the whole feries anew ; and as the deductions in this 
Report will be taken chiefly from that laft fet of experiments, 
it is proper here to defcribe minutely the method obferved by 
Mr. Gilpin in his operation. This naturally refolves itfelf 
into two parts, the way of making the mixtures, and the way 
of afcertaining their fpecific gravity. 
1. The mixtures were made by weight, as the only accu- 
rate method of fixing the proportions. In fluids of fuch very 
unequal expanfions by heat as water and alcohol, if meafures 
had been employed, increafing or decreafing in regular propor- 
tions to each other, the proportions of the mafles would have 
been fenfibly irregular ; now the latter was the objeCt in view, 
namely, to determine the real quantity of fpirit in any given mix- 
ture, abftraCting the confideration of its temperature. Refides, if 
the proportions had been taken by meafure, a different mix- 
ture Ihould have been made at every different degree of heat. 
Rut the principal confideration was, that with a very nice ba- 
lance, fuch as was employed on this occafion, quantities can be 
determined to much greater exaCtnefs by weight, than by any 
practicable way of meafurement. The proportions were, there- 
fore, 
