M. Haidinger on the Original Formation of Aerolites. 449 



teoric iron of Tula, containing imbedded fragments of meteoric 

 stone, discovered by Dr. Auerbach, proves beyond all doubt the 

 occurrence of larger iron-masses in veins, and of their including 

 fragments of the adjacent rocks*. 



In his paper " On Meteorites in Meteorites " (Poggendorff 's 

 Annalen, 1860, vol. cxi. p. 353), Baron Reichenbach examines 

 the mechanical composition of meteorites, paying particular 

 attention to their rounded or angular particles, these last cha- 

 racterized as "fragments, broken and rolled pieces, and pebbles" 

 (loc. cit. p. 384). Thirty-two meteorites (? stones), microscopi- 

 cally analysed, presented in their intimate or mechanical compo- 

 sition five distinct different substances, viz. sulphuret of iron 

 (pyrites), native iron, oxidulated oxide of iron (magnetite), a 

 grey, and a black substance f. Leaving aside some peculiarities 

 in the terminology employed by Baron Reichenbach, as well as 

 his criticism (p. 379) on the expression "secretion," stated 

 to have been used by myself, while in fact I prefer the more 

 neutral term "included substances," I could not give a better 

 mode of considering in detail the structure of meteorites than 

 has been rendered by Baron Reichenbach himself; and indeed 

 the scientific world is obliged to him for it. There we have the 

 character and nature of "meteoric tufa" pursued into their mi- 

 nutest details, indicating successive formation by the junction of 

 the more intimate atoms of " cosmical dust," — though, and this 

 is the very foundation of either mode of consideration, this took 

 place not within the vaporous dust freely dispersed through cos- 

 mical space, but within an already pre-existent and voluminous 

 agglomeration, in which mutual attraction only became effective 

 by producing real or absolute pressure. I really feel obliged to 

 Baron Reichenbach for these statements, although undertaken 

 with other intentions than to illustrate my own views on this 

 matter. 



The influence of solar heat has purposely been neglected in 

 the preceding considerations, on account of the want of an atmo- 

 sphere, in the strict sense of the term, in those spaces within 

 which the formation of meteorites (in their initial condition or 

 movement) may be admitted to take place. We know the tem- 

 perature of planetary space to be far below that of the freezing- 

 point, and we may assume an identical condition for the entire 

 orbit of our globe, with a radius of 95,000,000 miles, as well as 

 for the spaces beyond the orbit of Neptune (thirty times the 

 distance of the Earth from the Sun) ; and even still further, 



* See Haidinger's paper " On the Tula Meteoric Iron/' I. c. note ante. 



t These black and grey substances must refer to stony particles. I think 

 Reichenbach's list might be extended so as to include magnetic pyrites 

 (pyrrhotine), as well as a white substance. — R. P. G. 



