EXTREMES OF TEMPERATURE. 39 



a more or less starving condition. The comparative immunity 

 from the effects of cold shown by the more or less well-bred 

 horses we have been considering, is of course surpassed by that 

 possessed by animals which have no Eastern blood, and which 

 have been inured from their birth to very low temperatures, 

 like the Kirgis, Himalaya and Manchuria ponies. 



A form of cold which the skin of a horse can badly with- 

 stand, is that which is produced by using common salt to 

 melt snow, as is sometimes done during winter, in order to 

 clear snow from streets, so as to save the trouble and expense 

 of carting it away. A combination of snow and common 

 salt acts as a freezing mixture, which with, say, equal weights 

 of these two substances, has at the time of melting a tem- 

 perature of about o F. Consequently, if such a fluid comes 

 in contact with the feet and pasterns of a horse, it will be 

 liable to produce frost-bite by the direct application of great 

 cold to the skin of the part. In ordinary circumstances, 

 water cannot be colder than 32 F. Hence, when a horse is 

 travelling over ground covered with snow, its particles will be 

 prevented from coming in contact with the skin, by the hairs 

 of the part forming an obstacle to the entrance of these solid 

 bodies. Also, the air imprisoned between these hairs will 

 greatly aid in the defence of the skin, by the fact of air being 

 an extremely bad conductor of heat. Besides, the air con- 

 tained in the snow, as we have already seen (p. 32), renders 

 snow a far worse conductor of heat than water, or than ice 

 which is more or less free from air. Therefore, horses which 

 travel through a solution of snow and salt, will be much more 

 liable to frost-bite of their extremities, than if, under similar 

 conditions, they were to go through snow, say, of a tempera- 

 ture of 20 F., which is a degree of cold far below that ever 

 experienced in England. I have found in Northern Europe 

 during winter, that when the temperature of the air falls 

 below, say, 5 F., snow which had been subjected to traffic, 



