C 389 ] 
XXIII. A Second Paper on Hygrometry . 
By J. A. De Luc, Efy. F. R. S. 
Read July 14, 1791. 
PART II. 
I N the fir (t part of this Paper * I have treated of the funda- 
mental principles of hygrometry, and of feme hygrofcopic 
phenomena ; and this will relate to a particular application of 
thofe premifes. 
62. Since the publication of my fir ft hygrometer, many 
others have been invented, two of which are now principally 
in ufe ; the hair hygrometer of M. de Saussure, and my 
hygrometer made of a Jlip of whalebone , If the comparative 
points of thofe inftruments could be determined in the whole 
extent of their feales, the only inconvenience of their being 
both ufed would be, the neceffity of reducing to one of them, 
the obfervations made with the other; but from 70 to 1 00 of 
mine, which fpace includes the molt important period of moif 
iure , their correfpondent indications are as different from one 
another, and as variable, as if they were the effe£ts of two very 
different caufes. Therefore it is important to decide which of 
them fhould remain our only meafure of moijlure , till, if pof- 
fible, a better one is found. The following pages, I hope, 
will lead to that decifion. 
# Sec Page 1* of this Volume. 
2 63. The 
