454 



Marvels of the Universe 



surface, though smooth, is very irregular, and pieces appear to have been gouged out of it as it was 

 flying tlirough space, reminding us on a large scale of the frost-chippings which are noticed upon 

 many flints. The second meteorite referred to is from Otumpa, in the Argentine, and this weighs 

 even more than the former, turning the scale at fourteen hundred pounds. 



These smooth-surfaced specimens are very different in appearance to others in which the surface 

 has readily corroded from exposure to the atmosphere. Such an one is that enormous mass which 

 fell at Cranbourne, near Melbourne, which weighs no less than three and a half tons. The rusting 

 of the surface is remarkable, and small pieces appear ready to flake off at any moment. Unlike 

 the dark though shining appearance which characterizes so many of the meteoric irons, this one is 

 of a reddish colour. It stands in a special case at the Natural History JMuseum. One can only 

 imagine what were the concomitants of the fall of a mass such as this. It must have been con- 

 siderably larger when it first sailed 

 into the thin atmosphere a hundred 

 miles above the earth's surface. 

 Then, as it rushed along with a com- 

 mencing velocity varying from ten to 

 forty-five miles a second, we can see 

 its surface becoming scorched by the 

 great heat evolved by friction with 

 the atmosphere, giving rise to numerous 

 detonations as it compressed the air 

 in front of it into great wave-like 

 disturbances. Then, finally, it be- 

 came so retarded by the resistance of 

 the air that by the time it reached 

 the earth its initial velocity was lost, 

 and it merely fell, as would an 

 enormous stone dropping from a 

 position of rest on the outskirts of 

 our atmosphere. The air thus acts 

 as a veritable armour, protecting us 

 from bombardment from the outer 

 spheres. But even the striking of the 

 earth at a velocity of but a mile a 

 second might be enough to do con- 

 siderable damage, and a stone which 

 fell in Finland, in igoi, at a rate, it 

 has been calculated, of five hundred and eighty-four feet a second, made a hole in stiff loam of 

 about twenty-two inches. On the other hand, several stones which fell on the ice, a few inches 

 thick, at Hessle, near Upsala, in 1869, rebounded without damage either to the ice or to 

 themselves. 



The greater the trail left behind as a meteor sails across the skj', the greater has been the fusion 

 of its surface. This fusion appears to affect but the thinnest possible layer of the meteor, and 

 with the exception of this thin layer it is intensely cold. It has no heat whatever as it sails 

 through space, and the few seconds of friction with the air is insufficient to heat it to any great 

 extent, since allowance has to be made for the heat carried away from the mass by radiation into 

 the cold air. But the sudden generation of heat causes the fusion and luminosity of the outer layer, 

 and as one layer is carried away as a luminous haze, another layer is acted upon in the same way, 

 and in some cases the trail may develop into a luminous cloud, from which the meteorite is seen 



Pholo iy] [H. J. Sliepslone. 



THE SELMA METEORITE. 



The present weight of this Meteorite is 306 pounds: but it must have 

 been considerably greater when it first sailed into the thin atmosphere 

 one hundred miles above the earth; then its velocity would cause friction 

 that would scorch and wear away its surface. 



