The Hypothesis of Hanu. 43 



To this hypothesis of Dr. Haiiii, ascribing the genesis of storms 

 to the general circulation of the atmosphere, no application of 

 the laAvs of dynamics has yet been made with a view of develop- 

 ing it into an acceptable "theory." If it should be established 

 it does not follow that it will in any way affect the truth of the 

 commonly accepted " convectional system," which, founded as 

 it is on the well-known laws of thermo-dynamics, is not likely 

 to be successfully assailed. There may be an improved nomen- 

 clature for the laAvs of statics and dynamics that will express to 

 the mind more clearly the relation of cause and etfect ; but until 

 the advance of scientific research modifies the present formula- 

 tion of these laws the convectional theory Avill be generally ac- 

 ceiDted as giving the true interpretation of all the phenomena to 

 which it could be applied. 



Professor Russell, in commenting on this subject, expresses the 

 opinion that the low temperature is due to the convective inter- 

 change of air at a low temperature in the upper strata with air 

 of a high temperature in lower strata, such convective inter- 

 change tending^to make the whole body of air of a temperature 

 coinciding throughout with the adiabatic rate of upward dimi- 

 nution, with the consequent result of rendering the air at the 

 surface of the earth cooler than previously and the upper air 

 warmer. When the upward diminution of temperature is less 

 than the adiabatic rate, in the forced circulation of air crossing 

 a mountain ridge, there occurs the dynamic heating which is 

 obser'^^ed in the case of the foehn winds. The low temperature 

 near the earth he does not believe could ever l)e entirely produced 

 by nocturnal radiation from the ground. The high pressure, in 

 his opinion, is largely the result of greater density due to low 

 temperature, as is verv clearly indicated by the fact that the 

 temperature is almost inversely proportional to the pressure, and 

 that the places of lower temperature substantially coincide with 

 the places of greatest pressure. 



In advancing hypotheses and inviting discussion the real ob- 

 ject is, or at least should be, to discover the essential cause or 

 causes which determine the initial formation and subsequent 

 maintenance and progress of the cyclone. Some real progress 

 in charting lines of equal density seems to have been made by 

 M. Nils Ekholm following Professor Abbe's system of "' isostaths," 

 one using the term density, the other buoyancy. Professor Abbe 

 also introduces the factor of the orographic gradient, but the 



