APPENDIX. 43 



granite rocks in sandy deserts are polished by sand-flows far from 

 water. It has been suggested that the polish arises from the 

 action of silicated water, as the hollows in the pebbles are as 

 smooth as the general surface. But they are only in the condition 

 of the greatest part of the surface drift all over the interior of 

 New Holland. Unless therefore we assume that a flood of 

 sUicated water has covered the greater part of New Holland we 

 cannot so explain the phenomenon.* If, on the other hand, the 

 gems and the iron belong to the basaltic rocks, and if these are 

 younger than the cement, such an explanation can only be 

 accepted in connection with a much more distant origin for the 

 pebbles than any local strata. The older drift therefore cannot 

 have a local origin. 



It is certain, moreover, that if the other gems have been 

 derived from basaltic rocks, and not from the greenstone, of 

 which there is no evidence, the basalt was of an older period than 

 that which now covers the drift, and such older basalt is not 

 traceable. All therefore favours the belief that the term drift, 

 implying a driving of material from a distance, is a correct term 

 to apply to the diamond-bearing deposits ; but a question of 

 another kind immediately suggests itself : Was the motive power 

 of this drift, and of necessity of the gold drifts, fluviatile or 

 glacial ? A marine accumulation is not suggested ; and no fossil 

 remaias, favouring such a solution of the question, have been 

 found. Silicilied wood of the Carboniferous age occurs abund- 

 antly in the drift ; but it must have been silicilied long before 

 any diamond could have been formed from the carbon which the 

 original wood contained, unless diamonds claim an antiquity as 

 high as that of the coal measures themselves, or even one higher 

 than theirs. In that case they must also be drifted, as well as 

 the minerals and rocks that are associated with them. 



This may be the final result of our inquiries, but there are 

 many who (as Mr. Taylor does) think the diamond is a product of 



* On comparing some specimens of cetacean remains and teetli of Carchar- 

 odon, brought more than forty years ago from the beach at Fehxstow, in the 

 County of Suffolk (which fossUs are certainly older than those in the crag 

 cliffs above, and appear not to have fallen but to have been drifted up from a, 

 probably miocene submarine bed to the eastward), I recognize the identical 

 Tcind and degree of polish on these tertiary relics as distinguishes the Cudge- 

 gong pebbles. This, at any rate, is an interesting fact, and may have some 

 bearing on geological inferences beyond the present use of it. In the super- 

 ficial local drift above the ferruginous sandstone beds about Sydney are 

 niimerous polished pebbles and fragments of the rock, which exhibit an 

 oxidized surface, but the polish in that case is probably due to very different 

 agency to that of a de'posit upon the pebbles, which is the theory of those who 

 regard the Cudgegong pebbles as coated by an infiltration of silica. The 

 miocene fossils on Fehxstow Beach have, in the presence of iron, more relation 

 to the Sydney fragments than to the drift pebbles of Cudgegong and the 

 interior — but there, for the present, the comparison rests. 



