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[ 53 ] of heat, may assist us in discovering those which are produced upon our bodies from the same cause.

104. The point 0 of my hygrometer, as I have before observed (44), is that of the extreme humi- dity produced by melting ice. It was therefore of some importance to know what difference there would be in this point, when the hygrometer should be plunged into warmer water This I endeavoured to find out ; and the following is the result of my firn inquiries.

105. The moment I took one of my hygro- meters out of melting ice, I plunged it into water at the heat of 4 degrees of the thermometer that I have called common. It fell suddenly four of its de- grees below the thread which marked its height in the melting ice, but immediately rose again, and in four minutes reached 8 degrees and a half above the same thread. Deducting 22 1/2 from the height for the dilation of the mercury (48), there will remain 14. Consequently the water warmed at 45 degrees of the common thermometer, really made the hy- grometer sink 14 degrees be low 0.

106. Half an hour after this, the water being at 38 degrees, I found the hygrometer no higher than 6 1/2, that is to say 61/2 - 38/2 =-12 1/2. Consequently the true point of humidity indicated by the hygro- meter was 12 1/2 below 0. Lastly, the heat of the water being reduced to 28 degrees the hygrometer was at 3 - 28/2 = -11. I was then obliged to put an end to the experiment, which I have not been able to take up again since, for want of leisure. But what