PHYSICS OF THE GLOBE. 137 



In the chapter on storms, he considers that there is some 

 reason to believe that the simoom has some special qualities 

 besides heat and dryness, warranting its name of the poison 

 wind, and that it should not be treated of merely as a case 

 of hot wind. 



The northwest wind of Calcutta advances from some point 

 between northeast and west, or even southwest. The wind 

 that precedes the rain is very cool, and is heralded by a sud- 

 den rise of the barometer. Wind pressures of fifty pounds 

 to the square foot have been recorded on these occasions. 



In the chapter on cyclones Ferrel's formula for gradients 

 is applied to the case of storms in the tropics ; and the angles 

 of incurvature of the wind are given for several localities in 

 the storm of October 15, 1874. 



The monthly distribution of 115 cyclones in the Bay of 

 Bengal throughout the year was as follows : 



January 2 



February 



March 2 



April 9 



Mav 21 



June 10 



July 3 



August 4 



September G 



October 31 



November 18 



December 29 



The origin of the cyclones, he finds, in accordance with his 

 own and Mr. Elliott's investigations, is the production and 

 ascent of a large quantity of vapor, which is condensed with 

 the liberation of its latent heat over the place of its produc- 

 tion, instead of being carried away to some distant region. 

 He considers that there is a consequent local lowering of the 

 atmospheric pressure, causing, or tending to cause, an in- 

 draught of air towards the place of minimum pressure. 



Mr. Blanford would seem to imply that the barometric 

 depression in the central portions of this region is mainly 

 due to the ascent of vapor and its condensation; but it has 

 already been shown by others that these alone can produce 

 only a very insignificant diminution of pressure at the earth's 

 surface; and the true explanation of the origin of the latter 

 involves the consideration of the inertia, centrifugal force, and 

 internal friction of the atmosphere. The volume closes witli 

 a very excellent chapter of suggestions as to subjects requir- 

 ing further investigation. 



Among the general treatises on meteorology there has 

 been published one in Italian the "Manual Nautico di Me- 

 teorologia," by Captain F. Viscovish, of the Austro-Hunga- 



