1871.] Proceedings of the Asiatic Society. 67 
caused the rapid evaporation of any water, either a deposit of dew 
or pools of water &c., exposed to the rays of the sun. Thus a 
rapid development of vapour began. But soon the air became 
heated, and its capacity for vapour increased more rapidly than 
the process of evaporation could supply vapour. This caused the 
air to become relatively drier. Like operations in the converse 
sense took place in the evening. Such results were more or less 
visible in the observations made at various places that had come 
under his notice, but necessarily each locality would have its own 
peculiar conditions, and would show a special set of changes. It 
was, he thought, in some such manner as this that all Meteorologi- 
cal phenomena should be looked into, with the intention of ascer- 
taining as far as possible the precise physical causes of their com- 
ponent elements. A mere record of facts such as was commonly 
put forward asa discussion of the Meteorological phenomena of 
any locality, could only be of use in a scientific point of view so 
far as it was thus treated, and he hoped that all observers would 
bear this in mind. 
The variations of the pressure of the atmosphere were next re- 
ferred to. Col. Strachey said that he had little doubt that the dou- 
ble tide was simply the result of the heating power of the sun on 
the atmosphere, though we did not distinctly know how the result 
was brought about. He remarked that the explanation of the 
phenomenon involved the solution of a very difficult problem in hy- 
drodynamics, and that he believed that it was only by the aid of ma- 
thematical science that any precise explanation could be given. He 
regretted his own want of mathematical knowledge and hoped that 
some of the mathematicians of India or Europe might be led to in- 
vestigate the problem. It was, to ascertain the effect produced, (on 
an elastic vapour atmosphere covering a sphere), by a source of 
heat gradually moving round the sphere. The necessary result of 
such a process could be generally stated with great ease, but its 
precise mathematical expression was quite a different thing. The 
Sun, the source of heat, certainly caused the expansion of the por- 
tion of the atmosphere between the meridians say of 8 o’clock A. M. 
and 5 p, M., and a general overtlow of the upper parts of the atmos- 
pheric columns so expanded must take place to the east and the 
