the Fall of Meteorites on the Earth. 353 



of the atmosphere, as on these depend the changes of atmo- 

 spheric pressure nearer to the earth's surface, the causes of the 

 winds, &c. Whenever solid bodies move through them, so ab- 

 normal an event goes on with such enormous rapidity, that these 

 particles, quite isolated from each other, must be positively 

 pushed aside. In the van of the progressing meteorite a stra- 

 tum of atmospheric particles is formed, having no time to escape 

 before the progressing body, but by streaming back alongside of 

 it. « The velocity of a meteorite, supposed on an average to be 

 seven German miles (24,000 feet) per second, is to that of a 

 hurricane of 134*72 feet per second as 124*4 to 1. Suppose the 

 pressure to increase in the same proportion, it would be per 

 square foot, for the hurricane =32*8 lbs., and for the meteorite 

 4080*32 lbs., or more than 22 atmospheres. 



It may be supposed that such a sudden compression (action 

 and reaction continually remaining equal) must have the same 

 effect as the compression of air in the old tinder-boxes alluded 

 to by Prof. Benzenberg. It might not here be out of place to 

 quote in extenso a passage from a book published fifty years 

 ago*, expounding views still far from being cleared up : — 



" The incandescence perceived around fireballs in a state of 

 ignition may be the result either of combustion, although with 

 difficulty admissible in air so very rarefied, or of friction, as gene- 

 rally believed. I think it results still more from the compression 

 of air, as in our newly invented tinder-boxes air produces fire by 

 mere compression. Could not electricity become free in the same 

 way ? Suppose a cubic mile of air to be suddenly compressed 

 to a volume of one cubic foot, would not then the electricity 

 originally contained in it be set at liberty ? The circumstances 

 attending the explosion of igneous globes seem to be in accord- 

 ance with this supposition. These globes, when first seen, do 

 not appear larger than bright stars ; as they approach the ter- 

 restrial surface (generally in an oblique direction) they increase 

 to the size of the full moon, and at last, when at a few miles 

 distant, explode with a violent detonation. The cause of this 

 explosion is probably an excessive accumulation of electric matter, 

 streaming from compressed air into the igneous globe of about 

 3000 feet in size of (?) metallic substance. The distance being 

 still too considerable to admit of a discharge to the earth, this 

 takes place in the open air, or within a cloud. 



" Probably the place of the discharge depends less on the 

 proximity of the terrestrial surface than on the density of air re- 

 gulating the maximum of compression and accumulation of elec- 

 tricity. Subsequently to the explosion, the single fragments 



* Briefe geschrieben avf einer Reise durch die Schweiz im Jahre 1810, 

 von J. F. Benzenberg. 1 vol. Diisseldorf, 1811. 



