DR. BUTTON'S THEORY OF RAIN. 447 



the great discovery of Dalton and Gay-Lnssac, that vapor 

 in the atmosphere rests only on vapor, and thus forms an 

 independent atmosphere, and is not supported in the least 

 degree by the air. I imagined then, that vapor could rush 

 with great velocity from air where the dew point was high, 

 to air where the dew point was low. But when I discovered 

 that some rains were so great as to be beyond the power of 

 this theory too, I began to suspect the hypothesis itself, 

 which induced me to put it to the following trial. 



I united two glass retorts together by their necks, then 

 having covered one with snow, I put ten drops of water into 

 the other and placed it in a vessel of water at the tempera- 

 ture of 130, and let it remain in that situation seven hours, 

 the temperature of the room during the experiment being 

 about 70; not one drop was distilled over in all that time. 



I then took the retorts apart, leaving open the neck of the 

 one having the water in it; it has continued in the room, 

 open now for thirty days, with a temperature of 70 night 

 and day, and the dew point in the room never as high as 

 40, the ten drops of water .being now only slightly dimin- 

 ished. 



This refutes the hypothesis of rapid permeation of air by 

 vapor, and indeed, proves that vapor, like heat, when it 

 passes up to the upper regions, must be carried by the air, 

 and not thrust up by its own elasticity. But to return from 

 this digression; if the Huttonian theory is unable to pro- 

 duce such a rain as that at Wilmington, what will it do 

 with the one which occurred at Genoa, oh the 25th of Oc- 

 tober, 1822, when it rained thirty inches in twenty-four 

 hours ; or the one at Joyeuse, on the 9th of October, 1827, 

 when it rained thirty-one inches in twenty -two hours? 1 



Or how will it account for a storm of hail 2 which fell in 

 Orkney, on the 24th of July, 1818, in the afternoon, nine 



1 Pouillet, Elements de Physique, II, 758. a Edinburgh Trans. 1623. 



