xxiv TEMPERATURE OF WATER 137 



of the material, to which also smell and taste bear 

 witness. All substances, I may say in general terms, 

 tend to reproduce the qualities of the medium by 

 which they have been warmed. If you are surprised 

 at sulphur warming water, you have only to pour 

 water over quicklime ; it will at once evolve heat. 



XXV 



SOME waters are fatal, although they give no in- i 

 dication of this either by smell or taste. In 

 Arcadia, near Nonacris, the river called by the 

 people there the Styx lures strangers to ruin, as 

 its appearance and smell rouse no suspicion. This 

 is like the drugs of accomplished poisoners, which 

 cannot be detected save by their fatal effects. The 

 water I mentioned a little above brings destruction 

 with amazing swiftness, and allows no opportunity 

 of applying a remedy. It hardens immediately it is 2 

 drunk, and, much like chalk under the influence of 

 water, it sets and binds fast the bowels. There is 

 a poisonous water in Thessaly, near Tempe, shunned 

 by all cattle and wild beasts. It comes out through 

 seams of iron and copper, and contains the power 

 of softening the very hardest material. It does 

 not nourish any trees either, and it kills grass. 

 Certain rivers possess a peculiar and strange 

 power. Some there are whose draught dyes whole 

 flocks of sheep. Within a short time those that 

 were black have white fleeces ; in other cases those 

 that came white go away black. This is what two 

 rivers in Boeotia do, one of which from its effect is 

 called Melas (Blackwater). Both the rivers issue 

 from the same lake, to go on their opposite 



