On the Cyclones of the Bay of Bengal. 221 



T P 



— is substituted for T and — for P; and then they represent 



only one half of the motion, while T signifies the entire dura- 

 tion of a vibration. On the other hand, the trigonometric 

 series given by (31) agrees in substance with the series found 

 by Helmholtz, if, in the latter, % is understood as denoting 

 the time of the ascending motion of a single determined point 

 of the string. How this series in Helmholtz's work is ob- 

 tained does not appear to me to be clearly shown. For, appa- 

 rently, the letters x and % are at one time used for a variable, 

 and then again for a fixed point of the string ; and it does not 

 distinctly appear whether the mathematical development rests 

 upon the assumption of the law enunciated in no. 8 as valid 

 for all points of the string, or whether it is presupposed for a 

 single point only. The latter is done by Donkin and Lord 

 Eayleigh. But if the problem is to be determined, not only 



must y but also —■ be given as a function of t for the one 



point of the string. This uncertainty asserts itself in the 

 works mentioned by rendering it necessary, in the determi- 

 nation of % as a function of x 7 to go back to the observations. 

 Freiburg i. B., July 12, 1879. 



XXVIII. Cyclones of the Bay of Bengal *. By W. R. Birvr. 



IT is well known that the Bay of Bengal is a very dangerous 

 locality for our East-Indian shipping, especially the 

 head of the Bay in the neighbourhood of Calcutta. The 

 danger principally arises from the cyclones which sweep over 

 the Bay, wrecking ships and raising immense storm- waves 

 exceedingly destructive of human life. Thus in the year 

 1737, October 7, three hundred thousand people are stated to 

 have been drowned ; more than one hundred years later, in 

 1876, October 29 to November 1, one hundred thousand people 

 were drowned in Backergunge. In June 1822, fifty thousand 

 people perished by the storm-wave. In the year 1864, October 

 2 to 5, forty-eight thousand people were drowned in the 

 Hooghly by the storm-wave ; and in 1831, October 31, ten 

 thousand people were drowned by the storm-wave. In the 

 following year, 1832, May 21, between eight and ten thousand 

 people perished by the same agency. The total loss of 

 human life, as recorded in connexion with severe cyclones 

 that swept over the Bay on the dates given above, is no less 



* Report of the Madras Cyclone of May 1877, by J. Eliot, Esq, M. A., 

 Meteorological Reporter to the Government of Bengal. Calcutta, 1879. 



Phil Mag. S. 5. Vol. 9. No. 55. March 1880. R 



