108 Transportation of Masses of Matter hy Lightning. 



then, the weight or mass of the matter of lightning may be, if 

 we endow it with sufficient velocity (and its limit in this respect 

 has not hitherto been defined), we shall easily arrive, so Jar as 

 intensity is concerned, at all the singular facts which we have 

 accumulated, and shall afterwards detail. But these flashes of 

 lightning excite our interest not solely on account of their 

 power. It has also been remarked that the debris of bodies 

 struck with lightning, have sometimes, or, we ought rather to 

 say, have usually been violently scattered in all directions. This 

 circumstance will be very inadequately accounted for by any 

 explanation of the mechanical effects of lightning which shall 

 be based solely on the shock or the clashing of bodies ; but, 

 on the contrary, it will very readily comport with the hypo- 

 thesis that the lightning, by its presence, developes, in the very 

 substance of those bodies which it traverses, some fluid which 

 is eminently elastic, and whose power must evidently operate 

 in every possible direction. AVould any one hazard much, by 

 supposing that the elastic fluid in question is nothing else 

 than steam ? The matter of lightning melts, or at least, sud- 

 denly produces incandescence, in small metallic wires : may we 

 not hence conclude that it will also confer incandescence upon 

 any fine thread of water which it encounters in its passage ? 

 By consulting the table which M. Dulong and I prepared 

 concerning the elastic power of steam, it will be found that 

 it amounts to 45 atmospheres when water attains an elevation 

 of 260'' cent. (500° Fahr.) What, then, would not this power 

 be if the temperature amounted to the much higher one of 

 red-hot iron ? Such a power would be evidently sufficient, so 

 far as intensity is concerned, to explain every thing that is 

 known concerning the mechanical action of lightning. Those 

 who prefer a fact to a theoretical deduction, have only to con- 

 sult founders concerning the terrible effects which result from 

 the presence of a single drop of water in one of their moulds 

 at the time that the running flaming metal enters it, and then 

 he will very directly arrive at the same conclusion. If we sup- 

 pose moisture in the fissures and cells of common building stone 

 struck by lightning, the sudden development of steam would 

 break it, and the fragments would be projected to a distance 

 in all directions. Under the same circumstances, the sud- 



