48 Correspondence — Rev. T. G. Bonney. 



of metallic iron. If, as is surmised, these are portions of a shattered 

 planet (or of more than one such planets), then that planet must 

 have consisted of a metallic core, surrounded by a stony envelope, 

 affording a presumption that ours is similarly constituted. 



The question may be looked at from another point of view. We 

 know such bodies to be flying about in space ; and it is highly pro- 

 bable that our earth was formed out of a conglomeration of them. 

 It seems probable, then, that the materials of the earth were origi- 

 nally mingled fortuitously in a state of fusion, arising from the heat 

 developed by the collision. So long as the heat was sufficiently 

 great to keep the whole in a liquid state, in spite of the pressure 

 arising from the mutual gravitation of the parts, the heavier materials 

 would continue to fall towards the centre, and thus produce a metallic 

 core. But this process would possibly be imperfect in some parts, 

 either owing to the superficial portions being cooled to the limit 

 of the melting point for the^ pressure too soon for the precipitation 

 to be completed, or perhaps from meteorites arriving afterwards, 

 when the superficial layers had become too viscid for them to sink 

 through to their projDer stratum. Tlie subsequent contraction of the 

 whole beneath a cooled crust might, as I have suggested elsewhere,' 

 cause subjacent rock to pass into a fluid state, owing to decreased 

 pressure beneath mountain elevations, and thus basalt containing 

 metallic masses might be erupted. 



I wish that the report given in the Magazine had described the 

 forms of the masses of iron,^ which I believe are generally of a 

 similar angular character in most meteorites. 0. Fishek. 



TEREACES IN NOEWAT. 



Sib, — Allow me to express my regret to Colonel Greenwood for 

 having niisunderstood him, and to assure him that I did not write 

 withoiit his letters before me. The mistake, which I now see to be 

 my own, was partly due to my not understanding the word "inland" 

 in exactly the same sense as he had done, — a misunderstanding 

 caused to some extent by my experience in Norway, where terraces 

 which he would call "marine" occur some distance away from the 

 sea ; his reference to Glenroy also helped to increase the confusion. 

 In the other matter, we are using the word "cause" in a slightly 

 different sense. I know, of course, that in one case there is upheaval, 

 in another lowering of the river bed, but each makes the water run 

 quicker, and that — the running water — I have called the cause. 

 With this expression of my regret, both for having misunderstood 

 Colonel Greenwood and for being still unable to accept his theory, 

 I must occupy no more of your space on this matter. 



T. G. Bonnet. 



1 Cam. Phil. Trans., vol. xi., part iii. ; and Geol. Mag., Vol. V., p. 493, and 

 Vol. VI., p. 45. 



2 Nearly every stone meteorite preserves its true external dark vitrified coat; but 

 meteoric iron corrodes and rusts so rapidly on its exterior, that the original form of 

 the mass is seldom preserved.— Edit. Geol. Mag. 



