3^2 Mr. de Luc on 
law, to fufpeT the march of his hygrometer : which accidental 
complication I (hall explain hereafter. 
65. When I published thofe refults of my experiments and 
obfervations, 1 M. de Saussure rejedted them ; not from having 
made new experiments that had confirmed his opinions ; but 
becaufe he conjectured inverfely, that my theory refulted from a 
fallacious march of my hygrometer: and the well-earned 
reputation of that celebrated philofopher engaged me to 
undertake every experiment that could help me to detect on 
which fide was the error. I have related, in the firft part of 
this Paper, fome of thofe experiments; and now, for their 
application, as well as for giving an account of fome others, I 
ihall follow more particularly M. de Saussure’s procefs. 
66. In a large glafs vefl'el, containing (as 1 have mentioned 
above) a manometer and his hair- hygrometer, which veflel he 
had previoufly reduced to a known fmall diftance from extreme 
drynefs , M. de Saussure introduced from time to time a piece 
of wet cloth, which he weighed both before he put it into the 
vefl'el, and when he took it out. The fucceflive increafes in 
the quantity of vapour refulting from that procefs were indi- 
cated; on the manometer , by fuccelfive increafes in the quantity 
of the inclofed eiaflic fluids, which caufed the quickfilver to 
afcend more and more in that inftrument ; and on the hygro- 
meter, by fucceflive ixpanfions of the hair. The maximum of 
evaporation was clearly indicated by the manometer for, during 
every lading temperature, the quickfilver, after having afcended 
to a certain point, remained fixed at that point, notwith- 
ftanding a longer flay of the wet cloth ; and by repeating that 
operation at different temperatures, M. de Saussure determined 
the quantities of evaporated water that, in a given ipace, and 
bv a given temperature, produced the maximum of evaporation. 
] fa That 
