2^)6 Mr. de Luc on 
open air, he had inclofed it in the moijl vejfel , at a time when 
the place where it flood before had the degree of moijlure cor- 
refponding with the Jlationary ftate of that hygrofcope , he 
would then have obferved a phenomenon as little expe&ed as 
the former : for after that inftrument had been inclofed in the 
moijl vejfel, it would have moved, by that increafe of moijlure , 
in the fame direftion as it had done in the open dry air when there 
was on the contrary an increafe of drynefs , Surprifed no doubt 
at that phenomenon, M. ds Saussure would have fubmittcd 
his new inftrument to more experiments ; he would alfo have 
tried other threads , in which he would have found the fame fort 
of march, only at various degrees ; and if, in thecourfeof thofe 
trials, he had fubmitted the hair to the fame experiments, the 
fmallnefs of its motions backwards and forwards, and their irre- 
gularities, would not have prevented him from difcovering in it 
the fame fort of march as he had then been ufed to fee in other 
threads ; and thereby, he would have abandoned the whole 
tribe of threads as unfit for the hygrometer . 
y j. The whole of that fuppofed courfe of experiments with 
(libs and threads , is that which I have followed from the time I 
j i 
had abandoned the conftru&ion of my firft hygrometer ; which I 
did efpecially with the view of being able to try many fubftances. 
Therefore my theory was formed in confequence of the two 
above conclufions, which appear to me immediate, and fuch as 
M. de Saussure could not have drawn differently, if he had 
followed the fame neceffary fteps : and now I wall prove, more- 
over, that if it had not been for accidental circumftances in his 
own procefs, the hair alone would have engaged him by degrees 
to undertake the fame experiments. 
72. M, de Saussure’s firft hygrometers , having their index at 
the top of the frame, could be plunged into water ; and he 
tried 
