071 ttie Cause of Thunder, 99 



noise ; what result, then, may not be expected from the col- 

 lision of two enormous clouds ? Such in substance is the idea 

 which Seneca had formed concerning the noise of thunder. 

 (Qusest. Nat. lib. ii. §27.) 



Descartes, as it appears to me, has done little more than re- 

 peated the explanation of the author of Quctstiones Naturales, 

 and attempted to strengthen it by a comparison. " As to vio- 

 lent storms,**' he remarks, *' which are accompanied with whirl- 

 winds, thunder and lightning, those which I have been able to 

 examine, leave no doubt on my mind that they are caused in the 

 following manner : when it happens that a number of clouds col- 

 lect one above another, it is no uncommon circumstance Jbr the 

 more elevated to descend violently upon the lower ones, in the same 

 manner, as I remember formerly to have seen in the Alps, about 

 the month of May, that the snows being warmed and moistened, 

 and so made heavier by the sun, the slightest commotion in 

 the air was sufficient to cause the sudden descent of a great mass, 

 known under the name of an avalanche, which resounding in the 

 valleys, was not unlike the sound of thunder."*"* A single word, 

 however, is sufficient to demolish this explanation, viz.. It of- 

 ten thunders when there are not two strata of clouds in the at- 

 mosphere. 



Seneca and Descartes employ the alleged sudden approxima- 

 tion of two superimposed strata of air, in the condensation of a 

 certain bulk of air, whose dilatation again, equally sudden, pro- 



serene, the lightning struck iJie Ste-Lucie, a galley of three banks of oars, 

 where the Cardinal of AiTagon was dining, that it injured the rigging in 

 various places, killed two galley-slaves, as well as injured two other galleys. 

 The inquiry here occurs, did thunder attend the production of all this in- 

 jury, and on this point we have no information. Might not then the dam- 

 age result from the fall of aerolites ? This is a question it is now impos- 

 sible to answer. 



In the Memoirs of Forbin, we read, under date of the year 1686 : * When 

 the sky was very serene near the strait of La Sonde, we heard a loud peal 

 of thunder, similar to the noise of the discliarge of a shotted-gim : the 

 lightning loudly whistling past us, fell into the sea at about the distance of 

 two hundred paces, and continued to hiss in the water, making it boil up 

 for a considerable space of time. All these circumstances so very much re- 

 semble the phenomena which accompany the fall of a great aUrolitHf that it 

 is only natural to believe that the detonation, the hissing, and the boiliog 

 up of the sea described by Forbin, depended upon one of these meteoES. 



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