8 Mr. kirw an’s Experiments, See. on the fpecific Gravities 
2dly. That if bodies, fpecifically heavier than water, be 
weighed in air and in water, they lofe in water part of the 
weight which they were found to have in air ; and that the 
Weight fo loft is juft th$ fame as that of an equal bulk of wa- 
ter, and confequently that their fpecific gravity is equal to then- 
weight in air, or abfolute weight , divided by their lofts of weight 
in wafer. * 
jdly. That if a folid, ftpeciftcally heavier than a liquid,, be 
• weighed firft in air,- and then in that liquid, the weight it loftes 
is equal to the weight of an equal volume of that liquid ; t and 
confequently if fuch folid be weighed firft in air, then in water, 
and afterwards in any other liquid, the fpecific gravity of this 
liquid will be as the weight loft in it by fuch folid, divided by 
the lofs of weight of the fame folid in wafer. This method of 
finding the fpecific gravity of liquids I have found much more 
■exaft than that by the areometer, or the comparifoh of weights 
of equal meafures of fuch liquids and water, both of which are 
fubjefl to federal inaccuracies. 
4thly. That where the fpecific gravity of bodies is already 
known, the weight of an equal biilk .of water* may alfo be 
found, it being as the quotient of their abfolute weight divided 
by their fpecific gravity. - This I final! call their lofs of weight 
in water. 
Hence, where 'the fpecific gravity and abfolute weight of the 
ingredients of any compound are known, the fpecific gravity of 
fuch compound may eafily be calculated as it ought to be inter- 
mediate betwixt that of the lighter and that of the heavier, ac- 
cording to their feveral proportions : this I call the mathema- 
tical fpecific gravity. But, in fafl, the fpecific gravity of com- 
pounds, found by afitual experiment, feldom agrees with that 
found by calculation , but is often greater without any diminu- 
