130 On the Pitted Surface of Meteorites. 



and of hollows being formed at the spots where the crust en- 

 closed or was underlain by spherules of the sulphide. 



In general I see no reason lo believe that the oxidation pe- 

 netrates below the thin pellicle of oxidized crust or enamel that 

 perpetually forms over and protects the interior of the stone 

 or iron mass, and so often even encloses unchanged particles of 

 its most oxidizable ingredients. That the character of the pitting 

 which the surface of a meteorite undergoes does not depend so 

 much on the combustibility of its ingredients as on their mecha- 

 nical aggregation, seems further to follow from the fact that the 

 carbonaceous meteorites are not more pitted (generally, I think, 

 less so) than those which are free from carbon, while, on the other 

 hand, the more compact meteorites, but, I should add, also 

 those containing least of felspathic ingredients (the incrustation 

 of the more felspathic varieties being usually a once very fluid 

 glaze), are those which offer the most pitted surfaces. The 

 meteorites of Iowa, Gropalpur, Pultusk, and the marbled or 

 brecciated stones of Maza Koorna, Aldsworth, and Parnallee 

 may be instanced in confirmation of this ; while the softer and 

 less compact aggregates of meteoritic matter, of which the 

 Nellore and Busti meteorites are examples, present but little 

 pitting on their surfaces. 



I believe, then, that it is to the difference in the mechanical 

 facility with which the sudden heat penetrates the mass at dif- 

 ferent points on its surface, partly as a consequence of greater 

 conductivity, partly of greater fusibility, that the melting-out 

 and immediate dissipation in the air of the material at those 

 parts is mainly due, and that it is in no degree due to the 

 greater combustibility of the mass at those points. 



M. Daubree, on the other hand, does not believe that the 

 " pitting " is due to the sort of splintering effect of enormous 

 heat suddenly applied, because he has failed in producing an 

 analogous surface by plunging various kinds of rock into a fur- 

 nace at the Conservatoire des Arts et Metiers ; in which, how- 

 ever, the contrasts of temperature and mechanical means of 

 momentarily removing the fluid incrustation are absent from 

 the experiment, even if the characters of the rocks were strictly 

 comparable. M. Daubree, however, offers another explanation 

 of the phenomenon ; and this at least is one which it would be 

 difficult to refute by the repetition of the conditions in an ordi- 

 nary experiment. His view is, that the hollows formed on the 

 surface of the meteorite are produced by a sort of boring action 

 effected by the air compressed and fiercely agitated into gyra- 

 tory motion by the rapidly moving stone. " En tourbillonnant 

 ainsi sous de telles pressions, l'air tend a tarauder," he says, 

 and considers this mechanical action to be assisted by the che- 



