492 PLINY'S NATURAL HISTOET. [Book XXXI. 



summer, still less so in autumn, and least of all in times of drought. 

 River-water, too, is by no means always the same in taste, the 

 state of the bed over which it runs making a considerable 

 difference. For the quality of water, in fact, depends upon the 

 nature of the soil through which it flows, and the juices 42 of 

 the vegetation watered by it ; hence it is that the water of the 

 same river is found in some spots to be comparatively un- 

 wholesome. The confluents, too, of rivers, are apt to change the 

 flavour of the water, impregnating the stream in which they 

 are lost and absorbed ; as in the case of the Borysthenes, for 

 example. In some instances, again, the taste of river- water is 

 changed by the fall of heavy rains. It has happened three 

 times in the Bosporus that there has been a fall of salt rain, a 

 phenomenon which proved fatal to the crops. On three occa- 

 sions, also, the rains have imparted a bitterness to the over- 

 flowing streams of the Mlus, which was productive of great 

 pestilence throughout Egypt. 



CHAP. 30. HISTORICAL OBSERVATIONS UPON WATERS WHICH HAVE 



SUDDENLY MADE THEIR APPEARANCE OR SUDDENLY CEASED. 



It frequently happens that in spots where forests have been 

 felled, springs of water make 43 their appearance, the supply of 

 which was previously expended in the nutriment of the trees. 

 This was the case upon Mount Hsemus for example, when, 

 during the siege by Cassander, 44 the Gauls cut down a forest 

 for the purpose of making a rampart. Very often too, after 

 removing the wood which has covered an elevated spot and 

 so served to attract and consume the rains, devastating torrents 

 are formed by the concentration of the waters. It is very im- 

 portant also, for the maintenance of a constant supply of 

 water, to till the ground and keep it constantly in motion, 

 taking care to break and loosen the callosities of the surface 

 crust : at all events, we find it stated, that upon a city of 

 Crete, Arcadia by name, being razed to the ground, the springs 

 and water-courses, which before were very numerous in that 

 locality, all at once dried up ; but that, six years after, when 



42 See B. ii. c. 106. 



43 Ajasson remarks, that just the converse of this has been proved by 

 modern experience to be the case. 



44 The son of Antipater, then acting for Alexander during his absence 

 in the East. 



