[ 243 3 
Upon this it is to be obferved, that boerhaave’s 
method gave him the expanfion of his quickfilver, 
diminifhed by the whole expanfion nearly of the 
veflel which contained it. de luc’s gave him the 
expanfion of his quickfilver, diminilhed by the lon- 
gitudinal expanfion of the fcale applied to the ba- 
rometer, by which the height of the column was 
meafured. The vefifel which contained boer- 
haave’s quickfilver was glafs. The fcale of de 
luc’s barometer was deal, Glafs is confiderably al- 
tered in its dimenfions by heat ; deal but very little, 
in the direction of its longitudinal fibres : therefore, 
though M. de luc negledfed the expanfion of his 
fcale, the expanfion which he obferved of the quick- 
filver would be nearly the whole; but boerhaave 
muft have reckoned it much too fmall, negledting, 
as he fays he did, the expanfion of his glafs W; 
and the difference is no more than what the ex- 
panfion of the glafs will very nearly reconcile. 
boerhaave’s expanfion is too fmall, to be in pro- 
portion to M. de luc’s, by about _ T ‘ T of the 
whole volume, or fomewhat more than The 
expanfion of glafs, in length, by i8o°, is, as I am 
informed, about of an inch upon a foot, or 
part ; therefore, its expanfion in folid content, 
or volume, will be very nearly _L_, by i8o° ; and, 
by 2 i 2 °, about T i. T , or lefs than _4-_. 
(o) Sepojita ergo vitri interea dilatatione , &c. Thefe words 
may feem ambiguous ; but the meaning feems fufEciently deter- 
mined by what is faid, p. 173. 1. 2 — 5. 
I i z 
SECTION 
