Meteorites , and Volcanic Agency, 505 



iron enclosing the chondra, which in a microscopic section of 

 the stone present much the same appearance as the halo sur- 

 rounding the lunar disk ; similar appearances are likewise 

 to be often observed in the spherule itself. All tufaceous 

 meteorites have, disseminated throughout their mass, innume- 

 rable minute spangles of nickel-iron. These phenomena pre- 

 mise the reducing action of a gas ; and Daubree assumes that 

 ,hese changes have been wrought by hydrogen. The dis- 

 covery of hydrogen in the Lenarto meteoric iron by Graham, 

 and the fact of the presence of hydrogen in the sun, established 

 by Kirchhoff, support this view. An exposure to high tem- 

 peratures in such a case is, of course, likewise assumed. 



Distinct evidence of such exposure is, moreover, to be met 

 with in the case of meteorites which consist of fragments 

 cemented together with material of similar composition to 

 those fragments, as in the case of the stones of Orvinio and 

 Chantonnay *. Still, with the many proofs which we possess 

 of the action of heat, we have not yet met with a meteorite 

 which resembles a volcanic slag or a lava. Although the 

 meteorites are comparable to volcanic tuffs and breccias, this 

 comparison cannot be extended beyond a certain point. The 

 volcanic activity, of which the meteorites furnish evidence, con- 

 sisted in the disintegration of solid rock, in the modification, 

 by heat and otherwise, of already solidified masses. Outflows 

 of lava, and ejection of lava-glass and crystals, which, as Zirkel 

 has shown, form volcanic ash, have not taken place in the case 

 in question. 



It is, then, by explosive activity, and that alone, that the 

 breccias and tuffs which we find in meteorites have been 

 formed. We are here forcibly reminded of a similar terres- 

 trial phenomenon with which most are familiar, since in the 

 " Maars " of the Eifel we have what must rightly be regarded 

 as craters of explosion, and a proof that our earth also can 

 furnish an instance of volcanic explosive activity without 

 eruption of lava. 



The question which still has to be considered is, What is 

 the cause of that volcanic activity which has subjected the rock 

 forming the surface of such a star-mass to disintegration and 

 trituration, and by which the entire mass of a heavenly body 

 may gradually be reduced to fragments ? 



The question does not limit itself to what we have dwelt on, 

 but embraces a general consideration of cosmical volcanic 

 agency. Both on the sun and on our earth it is by means of 

 gases and vapours that volcanic energy is transmitted. On 

 the moon we find no traces of an atmosphere, which it would 

 * Sitzber. Akad. Wiss. Wien, vol. lxx. Abth. i. November Heft. 



