cxviii Journal of the Asiatic Society of Bengal. [N.S., XII, 



(3) The difficulties connected with explaining the permanent charge 

 on the earth were stated. It was shown that as the discharge current is 

 constant to the greatest heights reached in balloons, the renewal cannot 

 take place from electricity in the lower atmosphere. The possibility of a 

 very penetrating radiation carrying a negative charge was considered, 

 and the possibility of the spontaneous generation of negative electricity 



e 



in the earth caused by e being the variable and not m in the ratio — 



m 



which is a variable function of velocity, was discussed. 



(4) The question *' What is ball lightning ? " was next considered and 

 it was stated that " active nitrogen" as prepared by Prof. Strutt was 

 the nearest approach to ball lightning yet produced in the laboratory. 



(5) The great importance of Prof. Stormer's work on the aurora 

 was pointed out, and the consequences of Vegard's theory of the aurora, 

 which makes the aurora due to a ra> emitted by radio-active matter in 

 the sun were described. 



On Applications of the Kinetic Theory of Gases to Epidemio- 

 logical Problems. — By Major McKendrick. 



On the assumption that individuals interact amongst each other in a 

 random manner, it was shown how it is possible to obtain solutions of prob- 

 lems, which depended upon contagion, immunity, etc. Conversely if suit- 

 able statistics are available, it is possible to obtain information regarding 

 the mode of transmission of diseases — their tendency towards immunity 

 how they are affected by treatment — the degree of their epidemicity — their 

 single or dual nature — and whether they were on the increase or the 

 decrease. It was also shown how the notion of correlation arises naturally 

 out of the consideration of two dimensional phenomena of this nature : 

 and how there are two main typos of correlation, which differ from each 

 other fundamentally. 



The Mechanics of the Violin Bridge and Mute. — By 



C. V. Raman. 



The author discussed (with the aid of diagrams and lantern slides) 

 a mechanical theory he has developed which closely predicts the mode of 

 vibration of a string bowed at any given point with the specified pressure 

 and velooity. An important feature indicated by theory and verified 

 experimentally is that the bowed point does not generally move with 

 uniform velocity whilst slipping past the hairs of the bow. The effect of 

 muting on the vibrations of the violin-bridge wa> also shown. Prof. 

 Raman remarked that his observations made the correctness of the view 

 expressed by Giltay and De-Haas on the subject appear doubtful. 



Winds 



Monsoon. — Bv W 



The object of the work described in the paper was to examine the 

 monsoon currents at various heights above the earth's surface in relation 

 to the character of the large atmospheric circulation of which the monsoons 

 from a part, and also to discover any points requiring special attention 

 in connection with the research work with balloons recently started in 

 India. 



It was explained that the form of clouds enables one to estimate 

 their altitude, and thus observations of the directions and velocity of 

 movement of clouds furnish a simple means of examining the winds at 

 various heights above the earth's surface. 



