20 Proceedings of the Royal Physical Society. 



hoof becoming worn down by incessant and long-continued 

 action on the icy crust of the snow. We are accustomed to 

 hear of the cattle in long journeys in the Cape of Good Hope 

 and Australia becoming knocked up, and the traveller being 

 arrested in his journey by the failure of his beasts of burden. 

 I daresay many people entertain the idea (as I did myself) 

 that this knocking up was the consequence of physical exhaus- 

 tion on the part of the cattle. Mr Ford, one of the best zoolo- 

 gical draftsmen in Britain, first enlightened me on this point. 

 He had accompanied Dr, now, deservedly, Sir Andrew Smith 

 in one or more of his exploratory expeditions to the interior of 

 the Cape ; and he told me that this failure of the cattle was oc- 

 casioned, not by exhaustion, but by the actual wearing away 

 of the hoof, till blood oozed from it at every pore. The Cala- 

 hari desert was particularly obnoxious, as it is composed of a 

 slaty formation, highly inclined, which shivered easily off into 

 sharp fragments. It was like walking on bundles of pen- 

 knives, with their edges placed upwards. The cattle gave in 

 sooner in this desert than in any other district, in consequence 

 of the greater abrasion of the hoofs upon this slaty formation ; 

 and, till they grew again, the animal was useless, and scarcely, 

 even to crop its food, would it stir from the spot where it was 

 unyoked. I do not know what length of time would be 

 necessary to incapacitate an ox, — of course, it must be vari- 

 ous, according to the extent and nature of the ground tra- 

 velled over ; but although soft snow might protect it longest, 

 I imagine the brittle fragments of a hard frozen crust of snow 

 might be not much less destructive than the slaty splinters of 

 Calahari. 



I have examined the hair of the moose deer, and find that 

 its structure is the same as that of the rein-deer, which I 

 have already described in my paper last year. 



Alpine Hare (Lepus glacialis, Leach). — This beautiful 

 hare furnishes an admirable example of the adaptation of struc- 

 ture to habit. For heat and comfort nothing can surpass its 

 thick, delicate, white fur, which, on the under side of the 

 paws, assumes such a compact, double-plied, felt-like cha- 

 racter, that one would think no degree of cold could penetrate 



