6 Mr. de Luc on 
Haas, have made apparatuses of the fame kind, and I have 
made myfelf fome others of different fizes and (hapes ; and 
they all produce fenfibly the fame degree of drynefs. 
6 . The defcribed apparatus was ready in the month of Octo- 
ber, 1787, and I put in it one of my fir A hygrometers ; which, 
in a few days, came to its fixed point of drynefs , and there it 
has remained ever fince, though I have opened the veffel above 
four hundred times. That degree of conftancy, much beyond 
my expectation, has enabled me to make a variety of ex- 
periments, which elfe had been next to impoflible : it pro- 
ceeds partly from the great capacity of quicklime for molfiure , 
which I (hall determine hereafter ; and partly from its flownefs 
in receiving it ; which circumftances, added to the fmall fize of the 
openings, to their being at the top of the veflel, and to the care 
of putting in and taking out the inftruments nearly at the fame 
temperature, prevents the lime from acquiring any fenfible 
degree of molfiure during thefe operations. 
7. I did not truft at firft the apparent continuance of the 
fame degree of drynefs in that veflel. At the end ot nine 
months of frequent ufe, I began to fear, left the whalebone, 
of which the fandard hygrometer is made, had been impaired ; 
and I took it out, to try its point of extreme molfiure (of which 
I (hall (peak hereafter ;) but it came exaCtly to that point, and 
when put again into the lime-veffel it returned where it flood 
before. 1 have repeated many times that trial, with the fame 
refult ; the laft time was at the end of three years, when, 
inftead of a lofs of expanfibility in the whalebone , I found a 
fmall increafe, but probably accidental ; it went a little farther 
than its point of extreme molfiure, and came back to its con- 
ftant point of drynefs. 
8. The 
