544 Description and Analysis of a large mass of [Nov. 



We first attribute it to the more rapid oxidation of the part in con- 

 tact with the soil, but the legend says it was dug out of the ground ; so 

 that while it was interred, if it was altogether so, the whole would have 

 been equally subject to oxidation. When dug out and placed as an 

 object of worship it probably was kept under cover ; but the expression 

 and the account are altogether too vague to serve us as data from which 

 to deduce conclusions. It is doubtless possible (though but remotely 

 so) that the foot may have been formed by the gradual oxidation of the 

 lower part, yet this we should think — supposing the mass to have been 

 originally an egg-shaped lens, and as compact below as above — would 

 have gone on equallly over the whole of the lower surface, instead of 

 one part of it, and also at the large end (at c in Plate I.) but it has not 

 done this at all, and so, unless we also suppose unequal tendency to 

 oxidation, this process does not satisfactorily account for its present 

 shape, and this moreover, we cannot fairly suppose, because at present 

 the foot is as hard and as metallic as any other part. One supposition 

 only remains, i. e. that there might have been more of the scoriaceous 

 or earthy parts below, which have separated in time from the mass, and 

 the traces of these parts are, it is true, more frequent below and at 

 the rim of the disk than on the upper part. Yet this is very poor aid 

 to prove that there ever was so much more of it, as this supposition 

 demands, and it seems now as little liable to oxidation and decomposi- 

 tion as any other part, and if we admit this fully, still we have the ques- 

 tion of why the metallic nucleus (for such it would then be) has assum- 

 ed this shape ? which is in fact coming back to our original enquiry. 



I think one way of accounting for it may be this — 



If we suppose a ball of semi-fluid matter (whether rendered so from 

 heat or otherwise) to fall vertically to the earth's surface without break- 

 ing into fragments, such a mass would, it is clear, form a circular and 

 lenticular disk, which would be more or less flattened at the lower sur- 

 face ; for the motion of the mass would be then derived from a single 

 force, the earth's attraction, and the resistance would meet it in a line 

 directly opposed to that motion. 



But if we supposed our semi-fluid mass to fall in any line deviating 

 from the vertical, as in one for example like that of the arrow in Plate 

 XXIX, we have then altogether anew state of things ; for here are first two 

 forces in the mass, the vertical (from attraction) and the projectile force, 



