794 THE POPULAR SCIENCE MONTHLY. 



attention, was confined to his favorite West Indian storms, which 

 travel via the Gulf of Mexico. Espy reminded the public that 

 these were not the only great storms which visit the United States. 

 " There are rain and snow storms," said Espy, " which from No- 

 vember to March, at least, travel from west to east. These storms 

 are first heard of west of the Mississippi and sometimes as far north 

 as Iowa ; and they often travel from the Mississippi to the Con- 

 necticut in twenty-four hours." He concluded that these storms 

 must originate in the far West, at that time only a wilderness, and 

 so beyond the outposts of observation. Espy did not assert that 

 these storms differed in character from the ones with which Red- 

 field had dealt. He only reminded the world that the West Indies 

 were not the only place where storms were generated. In so doing, 

 he accurately pointed out the origin of a large proportion of 

 American storms. The storms which Bedfield studied were really 

 the least, in point of numbers, among the storms which visit the 

 continent. But Redfield's observations were confined to the sea- 

 board, so that he necessarily did not have his attention drawn to 

 this second class of great storms. Like many later Eastern men, 

 he did not realize what a prominent part the West plays in the 

 economy of the country. 



In two respects Prof. Espy became the critic of William C. 

 Redfield. He held that the winds related to great storms blow 

 radially to a center, either obliquely or directly. He also believed 

 that the depression of- the storm-center was caused, not by the 

 centrifugal force generated by the motion of the winds, as Red- 

 field was inclined to maintain, but was on account of the rarefac- 

 tion of the air through the heat developed by the condensation of 

 vapor in the form of rain or cloud. The latter theory proved of 

 more value than the former, and will stand as one of Prof. Espy's 

 additions to the meteorology of North America. The Western 

 origin of many storms and the function of heat in the develop- 

 ment of cyclones these are the two" contributions of Espy to the 

 science of American storms. 



Prop. Hare. But Espy's eyes were not sharp enough to see 

 all the facts about the origin and movement of our great disturb- 

 ances ; and so, as he made certain suggestions which added to the 

 value of Redfield's discoveries, his own in turn received amend- 

 ment. The chief of Espy's critics was that eminent American 

 scientist, Dr. Hare, whose queries in regard to Espy's conclusions 

 were pertinent and searching. He asked, among other things, 

 " whether agreeably to the observations of Franklin and general 

 experience confirming them, our storms producing northeasterly 

 winds do not travel from southwest to northeast ; whether their 

 traveling thus does not warrant the opinion that they originate 

 in the Gulf of Mexico : whether the observations of Redfield do 



