Prof. J. P. Espy on the Law of Storms. 347 



its latent caloric, expand the air in the cloud, spread out on all 

 sides, and roll out above at the top of the atmosphere, making 

 the barometer rise on all sides round on the outside of the cloud, 

 at a distance from the upmoving column in proportion to the 

 diameter of the cloud, whilst under the cloud the barometer 

 would fall ; and when the barometer falls one inch, the air will 

 be pressed up, in case an allowance is made for friction, with a 

 velocity of 240 feet per second. 



If the base of such an upmoving column as this were to 

 remain stationary over the same region, it would throw down, in 

 rain or hail, in a few hours ten times as much as is contained in 

 the air at any one time over the region of the rain. 



If vapour enough is condensed in a cloud to make one inch 

 deep of rain, it is plain that the same quantity of caloric is 

 evolved into the air which would be required to evaporate that 

 inch deep of rain into the air ; and it will be found by calcula- 

 tion that it will require 644,700 tons of coal to be burnt to eva- 

 porate the water which would cover ten miles square one inch 

 deep, on the supposition that one pound of coal would evaporate 

 13 lbs of water; and if the specific caloric of air is one-fourth of 

 that of water, this amount of coal burnt in the air would heat 

 the whole atmosphere from top to bottom 10^; for one inch 

 deep of rain is ^iigih of the weight of the whole atmosphere 

 over ten miles square ; and it is known by experiment that if one 

 pound of steam is condensed in 400 pounds of water it will heat 

 it 2i°, and the specific caloric of air being only one-fourth of 

 that of water, one pound of steam being condensed in 400 pounds 

 of air will heat that air 10 degrees. 



I say this to excite the philosophers in your country to exa- 

 mine my theoiy of storms. But fortunately the leading fact, 

 the in-blowing of the air, can be determined without studying 

 the theory, and that too with but little labour. 



The fact can be determined by the data furnished by exa- 

 mining the storms of Redfield, lleid, Piddington, and Thom. 

 (For the only storm of Thom which I have examined, see pp. 28 

 and 29 of my ' Fourth Report,' and for the others see p. 101 et 

 seq.) 



I find also in the storm of the Black Sea of Nov. 14th, 1854, 

 as laid down in the first Number of IMeteorological papers pub- 

 lished by the authority of the Board of Trade, that if arrows be 

 drawn representing the course of the wind at 10 o'clock, at all the 

 different places where the storm was violent at that hour, they will 

 all point inwards to a common centre, nearly about the south-west 

 side of the Sea of Azov. Perhaps by this time observations in 

 that sea may be obtained, and if so, I venture to predict that the 

 wind there waa from some eastern or north-eastern direction at 

 2A3 



