136 ANNUAL RECOED OF SCIENCE AND INDUSTRY. 



teorology, and is very graphically presented in the second 

 chapter. In the chapter on radiation and temperature, he 

 states that the predominating feature of Indian meteorology 

 is the semi-annual reversal of the system of winds, the primary 

 cause of which is the variation in the quantity of solar heat, 

 which is then followed out in all its details. From paragraph 

 62 we extract the folio wins: : "The maintenance of an ascend- 

 ing convection current over India in the rainy season, and of a 

 descending convection current in the cold dry season, is in both 

 cases consistent only with a vertical decrement of tempera- 

 ture less rapid than in regions where no such movement is in 

 progress." In the chapter on atmospheric pressure and winds, 

 Mr. Blanford first explains the laws that have been known as 

 Dove's law and Buys-Ballot's law, as particular consequences 

 of Ferrel's law. In the section on Indian monsoons the tables 

 and diagrams showing the monthly variations of tempera- 

 ture, pressure, wind, and clouds are extremely satisfactory. 

 He finds that the depth of the winter monsoon in January 

 and February in the neighborhood of the hills is probably 

 less than VOOO feet, while the summer monsoon is much 

 more than 11,500 feet. The summer monsoon has a greater 

 average velocity, depth, and volume than that of the win- 

 ter, but a lower velocity than the winds of the hottest sea- 

 son. During the height of the southwest monsoon there is a 

 region in the Arabian Sea in which the winds are light and 

 the sea smooth : this is known to navigators as the soft 

 place in the monsoon. To the north of this the monsoon 

 blows with great force. 



The diurnal barometric oscillations are given for a num- 

 ber of stations, and the theory that Mr. Blanford proposes 

 is ingenious, if not satisfactory. It is that originally worked 

 out by Kreil and Lamont, modified by the fundamental as- 

 sumption that the pressure exerted by the expansion of the 

 lower layers of the atmosphere is only slowly communicated 

 to the upper layers, and that the inertia of the latter, when 

 once in motion, accounts for the barometric minimum in the 

 afternoon. In the chapter on hygrometry, cloud, and rain- 

 fall, Mr. Blanford gives some comparisons between Wolf's 

 sun-spot numbers and the register of rainfall at six stations 

 in India since 1813. lie finds the cyclical variation of the 

 rainfall very distinctly indicated, especially from Madras- 



