?8 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



if the energy of the meteor increases or diminishes the cur- 

 vature of the trajectory will rapidly increase or diminish. 

 Second, the energy of the meteor is greater in proportion as 

 the air which it draws in is dryer, or has a low relative hu- 

 midity. 



In reference to the rigidity of the column of the water- 

 spout, Couste says that the equilibrium between the reacting 

 forces due to the radiating filaments exists even when the 

 various diameters of the waterspout are made unequal by 

 the pressure of the wind. The normal components of the 

 movement of the wind have the effect substantially of press- 

 ing the helicoidal filaments together normally to the surface, 

 thus concurring to maintain the rigidity of the column, to 

 which the gyratory movement contributes. This we can 

 easily comprehend if we compare the column to the gyro- 

 scope of Foucault; for the column of the waterspout can be 

 likened to a series of gyroscopes having a common vertical 

 axis, the revolving disks being formed by parallel horizontal 

 sections of the column. In the case of the tornado the disks 

 are gaseous, it is true, but the gas is kept in its place by the 

 normal components of the forces; and if they have but little 

 mass, they are, on the other hand, actuated by very rapid ve- 

 locity of rotation. 



Theoretically, a waterspout is a collection of parallel whirl- 

 ing tubular masses; a complete illustration of this is, how- 

 ever, very rare in nature, though such have been figured by 

 Mouchez and others. JYbuv. 3Leteorologiques i 1875, p. 61, 81. 



TREATISE ON METEOROLOGY BY MOHN. 



An important treatise on meteorology has lately been 

 published by Mohn, the distinguished chief of the Norwegian 

 AVeather Bureau. It constitutes an original German edition, 

 with many improvements, of the work published two years 

 ago in Norwegian, under the auspices of the Society for the 

 Dissemination of Useful Knowledge. As w r as to be expect- 

 ed, Mohn has especially developed in this work the ideas 

 that he has for some years defended with reference to the in- 

 fluence of moisture in the air upon the movements of storm 

 areas. His whole work, in fact, corresponds to the present 

 condition of meteorology, except, possibly, that the attempt 

 to provide a purely popular explanation of the mechanical 



