ON SPONTANEOUS EVAPORATION. gj 



them. Having done this, I found to my great satisfaction, 

 that these mean geometrical proportionals evidently repre- 

 sented the intermediate evaporations. Al! the experiments 

 I afterward made, the results of which ai-e given in the fol- 

 lowing table, confirm this law. 



The first column of this table contains the de2;rees of Explanation of 

 Mr. De Luc's thermometer*, at the temperature of which ' ^^ ^^ ^• 

 I made my experiments f. 



The third column contains the mean results of 291 expe- 

 riments, which I made to determine the ratio of evaporation 

 to heat, and the degree of spontaneous evaporation of wa- 

 ter at every degree of Mr. De Luc's thermometer from 0° 

 to 31°. To give the particular result of every experiment 

 would have been attended with little advantage, and occu- 

 jpied too much valuable room: accordingly 1 have divided 

 the sum of the evaporations observed iu every experiment 

 under the same degree of heat by the number of these ex- 

 periments, and given only the quotient, or mean result. 



The fourth column contains the evaporations calculated 

 according to the rule above mentioned ; that is, by insert- 

 ing 30 mean geometrical proportionals between the num- 

 bers expressing the evaporations observed at 0° and 31°. 



The fifth column gives the difference between the evapo- 

 rations thus calculated and the mean of those observed. 



In making these experiments I chose times when the ba- 

 rometer was about its mean height, which I determined by 

 l600 observations at my observatory, each day at noon, to 

 be 27 inches, 9'3 lines [29'56 in.], supposing the quicksilver 

 at the temperature of melting ice. 



* A second column is here added, containing those of Fahrenheit, 



C. 



f I made some other experiments indeed, and as far a| 40" of the 

 thermometer [ISS"^ F ] ; but as 1 have not yet been able lo repeat them 

 as often as 1 wl^^hed, 1 bave not reported their results. 



Thermometer, 



