ARTIFICIAL RAINS. 495 



miles around, and that rain follows it shortly, according to 

 immemorial observation in that country." 



"Very extensive fires in Nova Scotia, in the woods, are 

 so generally followed by heavy floods of rain, that there is 

 some reason to believe that the enormous pillars of smoke 

 have some share in producing them." [Mag. Nat. Hist, for 

 Dec., 1835.] 



The bad philosophy of supposing that smoke was turned 

 into cloud and produced rain, does not weaken the evidence 

 of the main fact. 



If the principle is correct, that clouds are formed by up- 

 moving columns of air, we should expect to find, in favor- 

 able states of the air, that clouds would form over large 

 cities and manufacturing towns where much fuel is burnt ; 

 and so we find it to be. 



Extract of a letter to me from Benjamin Matthias of Phi- 

 ladelphia : 



" In the course of the last winter, while in England, I 

 visited Manchester four or five times, and on each day it 

 rained. Several of the inhabitants assured me that it rains 

 in Manchester more or less every day in the year." 



Extract from Edward Mammatt's Collection of Facts 

 concerning Ashby Coal Field. 4to. London : 1836 : 



" When the air is apparently stagnant in the valley of 

 the Thames and surrounding country, a strong current is 

 found to set in, on every side of London, along the streets 

 leading from the country, in the morning. This current is 

 no doubt occasioned by the rarefaction in the high chim- 

 neys over so many thousand fires just kindled, and must 

 be the cause of the introduction of fresh air to an immense 

 extent, which would not otherwise flow. This rarefaction 

 produces other phenomena, among which, when the atmo- 

 sphere is in a light state, and clouds are passing at a height 

 which does not allow them to condense and fall in rain, 

 these accumulate in passing over London, and either remain 



