THE EFFECT OF HEAT ON ANIMALS 141 



Forest fly. In ordinary meadow -land cattle collect 

 under trees towards mid-day, and in the afternoon, if it 

 be possible, gather in the ponds, where they stand so 

 deep that the lower and most sensitive parts of their 

 bodies are completely covered by water. They thus 

 gain coolness and protection from insects at the same 

 time ; but there are not many field-ponds which are so 

 large or accessible from the bank that cattle can enjoy 

 themselves in this way, which, as Gilbert White 

 remarked, was equally good both for the beasts and 

 for the fish which gather round to catch the flies. 

 During the great drought two summers ago horses 

 became almost aquatic animals where this was possible. 

 They waded shoulder - deep in the Thames, eating 

 water-plants and seeking coolness, and, emboldened by 

 these excursions, even swam the river and invaded the 

 fields beyond. In the same year a small, deep pond in 

 a meadow beyond Hanwell, visible from the Great 

 Western Railway line, was used as a bath by four 

 horses for the greater part of each day. They stood 

 in it with the water almost level with their backs, and 

 presented the appearance of huge river animals of the 

 tapir kind floating in the pool. It seems clear from 

 this that they derive the same refreshment from the 

 application of cold water to the skin which other 

 perspiring animals do. Humane cab-drivers recognise 

 this fact by driving their horses as nearly as possible 



