24 Mr. De Luc on 
point. As for the exa£t ratio between the indications of thole 
la ft hygrojcopes, and the changes of moiflure, that was to be the 
objedt of a particular inquiry, to which 1 now come. 
Of the fcale of the hygrometer between the two fixed points. 
37. The long attention I had formerly given to the compa- 
rative expanfions by heat of various kinds of liquids and fohds, 
made me expedt the variety I afterwards found in the mo- 
difications of hygrofcopic fubftances by moiflure ; therefore, 
as I expreffed it in § 2. of my firft Paper, my view was only 
at that time, to find fome means of producing a fteady compara- 
ble hygrometer ; but afterwards I pointed out, in § 72, a means 
which had occurred to me, for attempting to find the ratio be- 
tween the expanfons of fome determined hygrofcopic fubftance, 
and the correfpondent increafes of moiflure ; which was, to com- 
pare the firft with the correfpondent changes of weight, of the 
fame or of any other fubftance ; an idea which I did not then 
much fcrutinize, not yet thinking of its execution. 
38. From what I have faid above, I did not want any other 
motive of choice between the ftps and the threads than their 
comparative marches ; but though the Jlips agree always in the 
direction of their motions, there are differences in the progref- 
fion of their comparative fteps ; and that difference led me to 
examine more attentively the above means of finding which of 
thofe marches agreed beft with that of moijiure. The refult of 
that examination was diftruft, at leaft in refpefl: of an imme- 
diate decifive means. With the view of rendering the changes 
of weight more eafily meafurable, I had firft thought of fome 
, fubftance pofleffed of a ftrong affinity with water ; but on con- 
fidering 
