^63 Sir GEORGE shuckburgh’s Qb/ervations 
freezing is = ~ 7 of the whole volume, at the tempera- 
ture 82° becomes ^ 4 — , a difference indeed that may 
fairly be neglected, and which I neglect myfelf; yet I 
cannot help obferving, in juftice to Mr. de luc, that his 
method of reducing his barometers always to the fame 
ftandard temperature, was free from the error I am 
fpeaking of. 
To conclude, the defeat of Mr. de Luc’s rules being 
fuppofed yl ll 5 , or, which comes to the fame thing, the 
correction being + when the temperature of the 
air is 6 i°. 4, and the true expanfion of the air for each 
degree being when the heat is 39°-7 ; required to 
find the temperature wherein the difference of the loga- 
rithms fhall give the true height in Englifh fathoms, 
that temperature, according to Mr. de luc, being 39°.74, 
and the expanfion r - 0 “ 3 00 . 
Let t be the temperature 6 i°. 4; s Mr. de luc t s 
ftandard temperature; e the expanfion for i°; e the fame, 
according to Mr. de luc; a the fuppofed correction of 
the rules, and x the temperature fought. We have then 
the following formula, t-s x e- e (i> — a = s-x, wherein 
proceeding with the above numbers s-x comes out 
(d) This fign is negative > becaufe the alTumed 'expanfion e is lefs than the 
true one e, and confetjuently tended to increafe the apparent error of the rules;, 
had it been greater, « would have been 4- . 
