110 THE METEORITES. — THEIR ORIGIN AND CHARACTER. 



taking an oblique direction towards the surface), or have irregularly barred structure, or 

 are granular. 



" These chondra bear no indications of having obtained their spherular form by crys- 

 tallization. . . . They resemble rather the spherules which are frequently met with in 

 our volcanic tuffs. ... As regards the last mentioned chondra, we know them to be the 

 result of volcanic trituration, and to owe their form to a prolonged explosive activity in 

 a volcanic ' throat,' where the older rocks have been broken up, and the tougher particles 

 have been rounded by continued attrition. The characters of the meteoric chondra indi- 

 cate throughout a similar mode of formation. ... It is certain, in short, that the sjjlier- 

 ules are the result of trituration. 



" The [meteoric tuffs] are peculiarly characterized as containing no trace of a slag-like 

 or vitreous rock, nor enclosing distinct crystals in the matrix ; in short they exhibit 

 nothing which their formation from lava would lead us to look for. All that is to be 

 seen in them is the triturated product of a crystalline rock. Some of the tufaceous 

 meteorites bear evidence of a later modification wrought by heat. . . . Others, again, 

 exhibit phenomena which can only be explained on the theory of their having under- 

 gone a chemical change subsequent to their formation. . . . 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 vol- 

 canic tuffs and breccias, this comparison cannot be extended beyond a certain point. 

 The volcanic activity, of which the meteorites furnish evidence, consisted in the disinte- 

 gration of solid rock, in tlie modification, by heat and otherwise, of already solidified 

 masses. ... It is, then, by explosive activity, and that alone, that the breccias and tuffs 

 which we find in meteorites have been formed. . . . The volcanic activity of which 

 those mysterious masses of stone and metal are evidence, may be compared to the violent 

 movements on the solar surface, the more feeble action of our terrestrial volcanoes, or the 

 stupendous eruptive phenomena of which the lunar craters tell the history. . . . Vol- 

 canic activity is a cosmical phenomenon in the sense that all star-masses at a stage of 

 their development exhibit a phase of volcanic activity." * 



The objections to the theoretical views of Tschermak, Sorby, Forbes, and 

 Maskelyne, can be briefly stated as follows : — 



The chondritic structure appears to be limited to meteorites of a peculiar 

 chemical and mineralogical character, while all, even of this special kind, do 

 not possess such structure. Hence, if it was purely mechanical, one can 

 hardly see how this structure could be so localized, not even being universal 

 for this special class. Again, if the spherules are the broken-up, and rounded 

 fragments of prior existing rock, they should have the composition of that 

 rock as a whole, instead of generally being composed either of olivine and 

 base, or of enstatite and base. Also, they ought to show in their interior 

 tlie structure of the rock from which they were derived ; while distinct 

 lines of demarkation, and a want of continuitj^, ought to exist between 



* Pliil. M;ig., 1S70 (5). i. 497-507 ; Sitz. Wioii. Akad, 1875, Ixxi. G61-G73. 



