Hygrometry . 
kinds of fubftances* I intend to repeat, and to have the honour 
of communicating their refults to the Royal Society ; and I 
fhail conclude this Paper, with an immediate demon ft ration, 
that the hygrofcopic motions of the flips are fimple, while thofe 
of the threads are the combined effedts of two oppofite caufes : 
which will be a farther confirmation of the whole of the 
ahove theory. 
On the recoil of hygrofcopic threads. 
58. When formerly I concluded from the phenomena of 
the Water thermofcope , that its condenfatiom were the combined 
effedts of two oppofite caufes, which followed different laws, 
it was not for having diftinguifhed thofe two effedts ; but only 
becaufe of a fmall retrogradation near the freezing point , preceded 
by a flaiionary ftate, comparatively with the march of quickfilver ; 
but in the cafe of hygrofcopic threads and flips , in which we 
have the fame phenomenon, the two oppofite effedts are diftin- 
guifhable in the threads , by one being operated more rapidly 
than the other. If, for inftance, I tranfport from a drier to a 
damper place (or inverfely) the two kinds of quill hygrofcopes, 
th ejlip proceeds in an even courfe to a certain point, where it 
remains fixed ; but the thread moves in an interrupted manner 
alfo to a certain point, whence it recoils. If that experiment 
is made within the limits of the ftationary ftate of the thready 
it may recoil as much as it has gone the other way, and be 
fixed at the fame point in both places. The cafe of the flip of 
quill is common to every flip , and that of its thread to all others 
which have a quick motion. Here then we ha wefeparately the two 
effedts of moijture on the threads ; that on the fibres themfelves 
is the fooneft produced, and at firft predominates : the fiowefl , 
bv 
