206 THE POPULAR SCIENCE MONTHLY. 



earth's internal forces may be as active now as in the epochs when the 

 mountain-ranges were formed. But Mr. Mallet's theory tends to show 

 that the volcanic energy of the earth is a declining force. Its chief 

 action had already been exerted when mountains began to be formed ; 

 what remains now is but the minutest fraction of the volcanic energy 

 of the mountain-forming era; and each year, as the earth parts with 

 more and more of its internal heat, the sources of her subterranean 

 energy are more and more exhausted. The thought once entertained 

 by astronomers, that the earth might explode like a bomb, her scattered 

 fragments producing a ring of bodies resembling the zone of asteriods, 

 seems further than ever from probability ; if ever there was any dan- 

 ger of such a catastrophe, the danger has long since passed away. 

 Spectator. 







GREAT FIRES AND RAIN-STORMS. 



BY JOHN TROWBRIDGE, 



ASSISTANT PROFESSOR OF PHTSICS 1ST HARVARD COLLEGE. 



THE belief that great fires are followed invariably by rain-storms is 

 wide-spread, and the great fires of the present year in America, 

 it is claimed, afford no exception to the law. The attitude of scientific 

 men in regard to so-called popular fallacies and superstitions is not, 

 in general, a praiseworthy one. A belief needs often only to be wide- 

 spread among the people at large to be denounced. Science is but an- 

 other word for truth, and even popular traditions deserve to be ex- 

 amined with care. The difficulties, however, in the way of an investiga- 

 tion of the effects of fires in producing rain-storms are manifold. Our 

 knowledge of the science of meteorology is, at the best, very imper- 

 fect ; and we have no series of observations from which we can draw 

 trustworthy conclusions. A careful search into the narratives of great 

 fires and into the accounts of great naval and land fights gives nothing 

 which a scientific man would accept for a moment. One who is ready 

 and determined to believe, it is true, will find in history many curious 

 and apparent corroborations of the truth of his belief. Thus in Pepys's 

 " Diary" there is a quaint and circumstantial account of the great fire in 

 London. In speaking of the progress of the fire, he says : " So as we 

 were forced to begin to pack up our own goods, and prepare for their re- 

 moval; and did by moonshine {it being brave dry and moonshine and 

 icarm weather) carry much of my goods into the garden ; " and in another 

 place : " But Lord ! what a sad sight it was by moonlight to see the 

 whole city almost on fire that you might see it plain at Woolwich, as 

 if you were by it." In still another place, in speaking of the poor suf- 

 ferers made homeless by the fire : "A great blessing it is to them that 

 it is fair weather for them to keep abroad night and day." He thus 



