TIMBERED MARGINS OF STREAMS. 47 



or else of bush. The courses of rivers indeed may 

 very generally be seen mapped out, in the distance, 

 by this fringe of timber; which thus acts as a guide, 

 to direct the traveller to a camping ground, where 

 those three great essentials, grass, wood, and water, 

 are to be found. At the end of a long march there- 

 fore, when evening is drawing on, or when the sky 

 indicates the approach of storms, the appearance of 

 these trees upon the horizon often forms a welcome 

 apparition to prairie travellers. In the icy winds too, 

 which periodically sweep over these plains, a ravine, 

 or other cosy nook, among these sheltering groves, 

 must at once be sought for; and the prudent traveller 

 will do well to mark, as he goes along, and keep in 

 his mind's eye, the location of such spots, to which in 

 case of need he may be able to fall back. * 



The shores of the larger lakes are, in the same way, 

 usually found bordered by woods and bush. On the 

 other hand, when the strand at the edge of these 

 sheets of water is seen perfectly clean, like the sea 

 shore, and the banks clear of timber, it very often 

 (though not always) indicates that the water is salt. 

 The presence too of flamingoes, is an almost certain 

 sign of saline waters, or marshes, which form the 

 constant haunt of these curious birds; which are sup- 

 posed to feed on particular sorts of worms, and other 

 insects, which live in vast numbers in the mud of even 

 the saltest lagoons, f 



* This practice of noting eligible spots for various purposes is one 

 which soon becomes second nature to leaders of parties travelling through 

 wild countries. In hostile neighbourhoods for instance defensible posts 

 and positions to which it may be possible to fall back in case of need 

 should invariably or studied and made careful note of. 



f Journal of Researches etc., by Charles Darwin, edition of 18/8, 

 p. 67. 



