90 Proceedings of the Asiatic Society. [Mar. 



falling water downwards and becomes thus mixed with the lower 

 current. At this stage we have the lower current, which is, to 

 use a convenient word, possessed of a velocity towards the north and 

 west, infiltrated by the upper cold current which is possessed of a 

 velocity towards the S. E. The resultant condition of the mixture 

 may be any modification of the storm velocity, even to quiescence. 

 Obviously, however, the air which comes down from above, must 

 always lose a very large proportion of its velocity, for it cannot 

 continue its forward course, without carrying with it the whole of 

 the air which remained undisplaced by the rain between the cloud 

 and the earth, and which had an initial velocity in the opposite 

 direction. 



My exjilanation shortly amounts to this, that the large body of 

 water generated and falling as the upper current passes on, pro- 

 duces the " Nor-Wester" by driving violently forward the air 

 which is displaced by it in its passage to the earth, while the air 

 which is not so displaced, is either brought to rest, or acquires a 

 comparatively small forward velocity (towards the S. E-) from the 

 upper current of air permeating it. If this explanation be correct, 

 and the facts occur as I have supposed them, they afford a remark- 

 able instance of transfer of motion. It would also follow from these 

 facts that the atmospheric pressure would increase during the pas- 

 sage of the storm ; for, in the first place, the advent of the upper cur- 

 rent of cold, and therefore relatively dense air, would, to some extent, 

 effect an addition of mass to the local atmosphere ; and secondly, 

 the two opposing currents checking each other's course, would 

 bring about a condensation of the air, which is the product of their 

 union. And it is some confirmation of my theory that, in truth, a 

 rise of the barometer does, I believe, uniformly occur during a 

 11 Nor- Wester." 



Also on the flanks of the storm there ought to be according to 

 the foregoing theory a strong wind, coming from the place of the 

 falling water. This would manifestly last as long as the storm 

 remained within a certain limited range, and would change its 

 direction as the storm passed by. As far as my observation has 

 extended, the phenomena which actually occur bear this out. 



