THEOEIES OF MEUXIER AND TSCHERMAK. 109 



possess types corresponding to rocks and structures of terrestrial origin, 

 i. e. to lavas, dunite, Iherzolite, serpentine, breccias, pumice, metallic veins, 

 metamorphic rocks, etc. David Forbes thus concisely gives the views of 

 the former : — 



" Meunier, who has of late written more copiously than concisely on the subject of 

 meteorites, whilst believing them to be fragments of broken-up planets, regards these 

 bodies as but the last stage in the evolution of planetary bodies, and suggests that the 

 moon is rapidly coming to this stage from the irregularities and incipient fissures visible 

 on its surface, its dissolution not having taken place before, owing to its greater magni- 

 tude ; argumg still further, that once broken up into fragments, these would arrange 

 themselves concentrically according to their densities, those which before formed the cen- 

 tral part of the planet, which he regards as most heavy and metallic, on the outside ; 

 and the others, according to their weight, in the interior. Tliis arrangement he considers 

 accounts for siderites or meteoric irons having first fallen in the earliest ages of the 

 world, then the siderolites [pallasites], and afterwards the stone or aerolites proper; and 

 owing to the meteorites of some recent falls, particularly that of Hessle in Sweden, hav- 

 ing contained considerable carbon, he predicts the fall of a totally different class of 

 meteorites in future. These hypotheses seem, however, to be but mere assumptions inca- 

 pable of proof, for although only some very few instances of siderites [siderolites] hav- 

 ing fallen in historic times are recorded, as compared to the much larger number uf 

 aerolites ; still there is no proof that the proportion was different in prehistoric times, 

 especially as it is well known that the latter would be infinitely more likely to escape 

 observation than the former." * 



Prof. Gustav Tschermak, in 1875, taught that meteorites were the result 

 of the disruption of cosmical bodies by explosive agencies. He stated that 



" the constitution of many of the meteorites shows that they are the result of a gi-ad- 

 ual tranquil crystallization ; while others, on the contrary, are composed of fragments, 

 and are the product of disintegrating forces. The majority are made up of minute flakes 

 and splmters and of rounded granules." 



Following Haidinger, he regarded the chondritic meteorites as tufas, and 

 states that the spherules have the following characters : — 



" 1. They are imbedded in a matrix consisting of fine or coarse splinter-like par- 

 ticles. 



" 2. They are invariably larger than these particles. 



" 3. They are always distinct individuals, never merging into each other or joined 

 together. 



" 4. They are quite spherular when composed of a tough mineral, and in other cases 

 merely rounded in form. 



"5. They consist sometimes of one mineral, sometimes of several minerals, bi._ 

 always of the same material as the matrix. 



" 6. The structure of the interior of a spherule is in no way related to its external 

 form. They are either fragments of a crystal, or have fibrous structure (the fibres 



* Geol. Mag., 1872 (1), is. 2131. 



