Hygrometry . 394 
gone over a great field of hygrofcopic phenomena, in which, 
the hair, and a clofe ve[Jel 9 had a (hare; and thereby, feeing 
the objects in another light than M. de Saussure, I doubted, 
of his conclufions, and I procured three, of bis hygrometers , in. 
order to examine them on fame particular points. It was after J 
that immediate verification of my conjectures concerning his 
inftrument, that I fettled the following conclufions, very dif- 
ferent from thofe above. 1 ft. That moisture, or the quan- 
tity of vapour fpread in the medium itfelf, does not increafe in 
an inclofed fpace in proportion to the quantity of water eva- 
porated in it ; becaufe of an increafing, but undetermined, part 
of that water being depofited on the fides of the veffel ; and 
that, confequently, Mr. de Saussure’s experiments could not 
afford the determination of a real hygrofcopic-fcalc , 2dly, That 
the ci remittance confidered by him as a fore fign of extreme: 
moijiure exifting in the inclofed medium , namely, the maximum 
of evaporation in the fpace, has only that effeCl when the tem- 
perature is very little above 32 0 ; but that, by fucceffive in- 
creafes of heat from that point, moijiure recedes farther, and 
farther from its extreme ; or from the point where no more 
vapour can be introduced in the medium without an immediate 
precipitation ; though at the fame time, there are fucceffive in*- 
creafes in the quantity of vapour , and thereby a conftant maxi- 
mum of evaporation correfpondent with the aClual temperature .. 
3dly, That, in approaching to extreme moijiure , th t hair hygro- 
meter becomes fationary , and afterwards a little retrograde , in 
which march the unavoidable irregularities of every hygrofcopic 
fubftance produce frequent anomalies; from which caufe it 
was very difficult for M. de Saussure, confidering the form 
of his experiments, to difeover the hygrofcopic law exprefied by 
the fecond conclufion ; and with the unknown exiftence of that 
tazv r . 
