DYNAMIC iMETEOROLOGY. 373 



meteorologist rather than an elegant analyst, lie is satisfied with show- 

 ing that the larger features of atmospheric motion are abundantly 

 explicable by known laws of mechanics and that, therefore, the ulti- 

 mate details of these phenomena will undoubtedly be also thus ex- 

 plained, and this conviction is that which is needed in order to attract 

 to this study those who wish to devote themselves to "exact science." 



The formula3 for cyclones are treated approximately for the case of no 

 friction and uniform temperature; then for the case of a difference of 

 temperature between the central and exterior parts, the warm center 

 being a cyclone, the cold center the anti-cyclone ; finally, the solution is 

 indicated for the case of the existence of both friction and temperature 

 disturbances. In the next section on the progressive motion of cyclones, 

 Ferrel states, on page 259, that " the i)rincipal cause of the progressive 

 motion is the general motion of the atmosphere ;" but he also adds that 

 "the velocity of progress is much greater than the general motion of the 

 atmosphere," and his short discussion of this subject suffices, we think, 

 to show that the cyclonic progress is only to a small extent actually due 

 to the general atmospheric motion, and is mainly due to those causes 

 that determine the distribution of vapor and precipitation around " the 

 center of power," as he terms it. By this precipitation and redistribu- 

 tion of heat, the cyclone center is, as Ferrel states, continually renewed 

 a little in advance of its former position. My own view differs from his 

 only in the relative effect attributed by us to the general movement of 

 the atmosphere on the one hand, and the tendency to the formation of 

 new aspiration centers on the other. Ferrel gives special prominence 

 to the former, but I to the latter; possibly he is correct for high south- 

 ern or northern latitudes, but my own view agrees best with my experi- 

 ence in the temperate zones; it appears to agree closely with the excel- 

 lent work of John Eliot in India, and is peculiarly applicable to many 

 abnormal storm-paths that I have had occasion to predict. I notice 

 that Ferrel, on page 260, quotes the lake region of North America as 

 possibly attracting cyclones by reason of the aqueous vai)or furnished 

 by them : but would it not be more rational to infer that the course of 

 our great storms is determined by larger forces than the slight excess 

 of evaporation over the lakes as compared with surrounding forest and 

 prairie; that in fact the lakes are the result of the precii)itation that 

 occurs from the atmosphere above them? Evaporation and moist air 

 are not of themselves able to produce a storm; we must have cold or 

 dry air ready to fiowin beneath, and our i)resent lake region (as well as 

 our ancient glaciated region) is so evidently located precisely in the 

 spot where cold northerly and warm southerly winds conspire with the 

 orography of the continent to produce precipitation and storms, that I 

 must consider the lakes (and glacial epoch) as the result of the orogra- 

 phy, and as exerting by their evaporation only a very slight reflex action 

 principally appreciable in there-distribution of local rains and snow 

 and slightly higher temperatures in their immediate neighborhood. On 



