[ *6 7 ] 
XIII. Remarks on fpectfc Gravities taken at different Degrees of 
Heat , and an eajy Method of reducing them to a common Stan- 
dard. By Richard Kir wan, Efq. P. R.. S. 
Read February 1 7, 1785. 
T HAT a comparative view of the weights of equal volumes 
of water and all other fubftances is highly ufeful on 
many occafions, is too well known to require any proof; but 
that a principal ufe refulting from this companion, when pro- 
perly made, is unattainable by a perufal of the common tables, 
I fhall here endeavour to (hew, and at the fame time point 
out a remedy for this defect. 
One capital advantage derivable from a table of fpecific gra- 
vities, is the knowledge of the abfolute weight of any folid 
meafu re of the fubftances therein contained, or that of the folid 
meafure of a given weight of thofe fubftances, a cubic foot of 
water being liippofed to weigh 1000 ounces avoirdupois, and 
confequently a cubic inch of water weighing 253,182 grains. 
But the authors who have difeovered this equation of weight and 
meafure, and all thofe who have ftnee treated this fubjedt, have 
negledled to inform us of the temperature at which this agree- 
ment takes place ; yet that it cannot take place in all tempera- 
tures is evident from the experiments of Dr. Halley and 
others, who have found, that from a few degrees above the 
freezing to the boiling point, water is dilated about of its 
bulk; and, confequently, if 1000 ounces at the freezing point 
be equal to one cubic foot, they muft be equal at the boiling 
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