102 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



results to the study of a few hurricanes. The mathematical 

 formulae by which he has endeavored to show the relation be- 

 tween the velocity and pressure of the air and the dimensions 

 of the whirlwind are apparently deduced in a not very rigor- 

 ous, but sufficiently approximate manner. On applying them 

 to the actual observations taken in connection with the hur- 

 ricane of 1837 (the so-called Antiguan hurricane), and also to 

 the hurricane of the 21st of August, 1871, he finds that the 

 formula represents the observations with a degree of accura- 

 cy probably within the errors to which the observations them- 

 selves are likely to be subject. The simple principle according 

 to which he is able to calculate the nature of the final shape 

 of the surface which is shown for instance whenever water is 

 allowed to flow out of a bowl through a central hole, consists 

 in this, viz., that when the rotation is once established in the 

 water, each particle describes a circle about the central axis, 

 whose radius is such that the pressure of the water above 

 the moving particle exactly counterbalances the centrifugal 

 force due to its circular rotation. In the case of the atmos- 

 phere we have, instead of a well-defined surface, a series of 

 surfaces of equal pressure, and the centrifugal force due to 

 the circular movement around the centre of the hurricane is 

 counterbalanced by the pressure of the atmosphere at that 

 point. Unfortunately, Mr. Colding seems not to have taken 

 account of the force due to the rotation of the earth on its 

 axis. His equations, therefore, apply to tornadoes and to the 

 central portions of hurricanes better than they do to the ex- 

 terior portions of large storms. Zeitsch. fur Meteorologie, 

 May, 1875, 133. 



THE MONSOON. 



In the magnificent volume of magnetic observations at 

 Trevandrum, in Southern India, Mr. Broun gives the follow- 

 ing interesting account of the advent of the monsoon. He 

 was stationed at certain times at an auxiliary observatory 

 on the peak known to the natives as Agustia, whose alti- 

 tude is over 6000 feet, and which from time immemorial had 

 been superstitiously regarded by the Hindoos as the resi- 

 dence of Agustia, a savant, physician, philologist, and theo- 

 logian, whose principles were celebrated for their purity. 

 Mr. Broun states that during his visits to this peak he made 



