M. Haidinger on the Original Formation of Aerolites. 453 



The subject of progressive changes in the world of meteorites, 

 as hitherto exemplified by specimens within our knowledge, is 

 thus for the present confined within narrow limits. Are these 

 progressive changes of a character likely to terminate the proper 

 existence of a celestial body by its definitive division into frag- 

 ments? or is the possibility of such a "breaking up" justified 

 by any precedent not opposed to the laws of nature as known to 

 us ? A few considerations made from this point of view may 

 serve to supply a real desideratum. 



I intend to sketch them here as briefly as possible, taking my 

 point of departure from a septaria, whose constitution I have 

 already explained. As in such a terrestrial concretion, so the 

 outward crust of a cosmical body may become solid, presenting 

 a stony appearance, under the centripetal pressure of gravitation, 

 long before its interior has undergone a like degree of compres- 

 sion. I take our own globe as a point of comparison for data 

 expressed in figures. Originally the particles of the solid ter- 

 restrial crust lying next each other may possibly have enjoyed a 

 certain amount of mobility ; this of course no longer exists. The 

 maximum of pressure has its seat at a depth where the greater 

 and more solid mass rests on the interior compressed by it in a 

 descending direction. We are entitled to suppose this under- 

 lying mass is maintained by this very pressure in a state of in- 

 candescent fusion. Atmospheric pressure represented by the 

 weight of a column of water 32 feet high, amounts to 1804'8 

 lbs. per square foot. A column of 10 feet average height otany 

 substance whose specific gravity is = 30, acts nearly with the 

 same degree of force. At the height of 1 German mile (24,000 

 feet) the pressure is = 2400 atmospheres ; at 5 miles (25 miles 

 English) (a measure generally adopted to express the solid ter- 

 restrial crust*) it would amount to no less than 12,000 atmo- 

 spheres. A solid pressing on our globe with the weight of 1 lb. 

 would in the Moon press only with T ^ lb., and if transported on 

 to the Sun's surface with 28^ lbs.f The pressure produced on 



Rose of Berlin, has proved beyond doubt the occurrence of quartz in iso- 

 lated crystals in the meteoric iron of Ziquipilco (Toluca).— W. H. 



It may be here mentioned that Berzelius, Rammelsberg, and Dr. Lau- 

 rence Smith have pointed out strongly and with much truth, the general 

 resemblance that meteorites, in whole or part, not unfrequently bear to cer- 

 tain volcanic rocks. See Dr. Buchner's work, Die Feuermeteore insbesondere 

 Meteoriten, Sfc, p. 175.— R. P. G. 



* Important and more recent researches on the question of the thickness 

 of the earth's crust, as conducted by Professor Hopkins and others in this 

 country, may necessitate our raising M. Haidinger's estimate of only 25 

 miles of a solid crust to something like a minimum of 300 miles. This is 

 more a question of degree, however, and does not materially affect M. Hai- 

 dinger's line of argument. — R. P. G. 



t Madler, loc. cit. pp. 577 and 556. 



