466 PHILOSOPHY OF STORMS. 



There is no doubt that such a thing as upward vortices 

 of air, and gradual ascensions of large tracts of atmosphere 



it would be fatal to my doctrine, so far as the barometer is concerned, and 

 then I would have to abandon the whole ground. But the fact is not so. 

 If the reader will turn to Col. Reid's late work on hurricanes, he will find, at 

 page 59, that the barometer fell at Porto Rico to 28 inches, on the passage of a 

 hurricane, and rose 1.17 inches in an hour and a half. And at page 269, the 

 barometer fell in the Bay of Bengal, in a tremendous hurricane, to 27.80 

 having stood at 29.70 at the beginning of the storm. And at page 271, the 

 mercury sunk out of sight below 26.50, having stood three hours before 

 over 29 inches. This was at the mouth of the Hoogly while at Calcutta, 

 about one hundred miles off, the barometer fell only three quarters of an 

 inch. (150, 151.) 



Now, as these great fluctuations occur in these latitudes only when a great 

 hurricane occurs, and are known to accompany the hurricane in its progress, 

 and are great in proportion to the violence of the storm, and are confined to 

 the region of the storm itself, and especially as it is now known that the 

 barometer rises on the approach of the borders of a storm, it seems almost 

 certain that the cause of the storm is the cause of the fluctuation, unless they 

 are related to each other, as cause and effect. (170, Table.) 



Indeed, if it is a fact, (and nothing is better established) that the barometer 

 does stand low in the middle of these great hurricanes, all the other phe- 

 nomena connected with them are mere corollaries. The wind will blow 

 inwards with a velocity proportionate to the square root of the depression of 

 the barometer; it will rise in the central parts of the storm in a similar ratio, 

 that is, with the velocity of about 240 feet per second for a depression of one 

 inch, without making any allowance for the rise of the barometer in an annu- 

 lus all round the storm, in consequence of the rapid efflux of air on all sides 

 in the upper part of the cloud ; and even the very quantity of vapor con- 

 densed per second may be calculated, if the dew point and depression of the 

 barometer are given ; and it is found adequate to produce those mighty floods 

 of rain which are known to fall in these storms. The quantity of rain which 

 sometimes falls in one of these hurricanes, over a limited space, is certainly 

 as much as ten inches ; in which sufficient caloric of elasticity is given out to 

 heat the whole of the air over this region, from the top of the cloud down to 

 the surface of the earth, more than one hundred degrees. But when it is con- 

 sidered that every portion of air which rises from the surface of the earth to 

 that height, undergoes a refrigerating process of more than one hundred de- 

 grees, from diminished pressure, and that it would actually become colder to 

 that amount, if it were not for the caloric of elasticity given out in the con- 

 densation of the vapor, which prevents it from cooling more than about half 

 this quantity, as I have demonstrated by experiment, it will no longer be a 



