488 KANSAS CITY REVIEW OF SCIENCE. 



to differences of temperature. If over a region of country the air be abnormally 

 hot, this region then being surrounded by cooler air, the hot air will begin to rise> 

 The condition of equilibrium may be reached without the formation of a whirl^ 

 but if the heated region is large, a whirl will be very likely to form at some point, 

 and the hot air will pour up through the vortex formed. The whirl may be the 

 result of the meeting of currents of air, and when thus produced may rotate eith- 

 er with or opposed to the motion of the hands of a watch. In the former case, 

 in the northern hemisphere, the whirl will gradually cease without becoming de- 

 structive, as the deflection of all moving bodies to the right in the northern hem- 

 isphere (by a force due to the earth's rotation) causes the wind to rush in more 

 and more nearly radially. 



The writer has seen one well-marked case of this kind. If the whirl is start- 

 ed in the reverse direction, and the unstable conditions are sufficiently wide- 

 spread, the tornado will result. In the latter case the deflection of moving bodies 

 to the right in the northern hemisphere will develop the whirl. As the air rises 

 in the vortex, it expands, and cools. Its moisture is condensed to rain and snow» 

 This snow is carried upward and outward, and finally falls down into the lower 

 winds which feed into the vortex, where it is again carried up, passing first into 

 a region where water is condensed upon it, which again freezes at higher alti- 

 tudes. This may be repeated many times for some of the hailstones, and they 

 thus acquire very large dimensions. Occasionally stones will jostle against each 

 other and freeze together, forming large masses. The action of the whirl throws 

 the stones into rotation either around the shorter axis of the hailstone, or around 

 the centre of the whirl. In general both rotations will exist at the same time, so 

 that Ferrel's explanation fully accounts for the discoidal or lens-like forms so 

 common in hailstones, and it also accounts for the fact that hail-storms run in 

 narrow belts. 



In the throat of the vortex there may be a large accumulation of water^ 

 held up by the ascending currents. The amount of water thus held will depend 

 upon the humidity of the air. It may be very large indeed, and the dispersion 

 of the vortex gives rise to the well-known "cloud-bursts," where the water has 

 been known to pour down in streams, washing holes several feet in depth into 

 the soil. Mr. Ferrel's paper is largely expressed in mathematical language and 

 seems to be somewhat unfamiliar to the general public, but it is certain that it 

 explains fully all the phenomena of the tornado and the formation of hail, and is 

 not open to any objection. He proves beyond all question that the effect of un- 

 equal temperatures is sufficient to account for the results, and this cannot be said 

 of any explanation before offered. 



Washington University, November 23, 1882. 



