274 Iw an d its Natural History 



edges and corners by the chemical action of weathering. 

 When gravity dislodges and brings them down into the 

 valley, they only require to be hurried along by one flood 

 to come out clean and round. In these places no one can 

 fail to recognise that the function of the river or stream is 

 mainly distributive. Now, whether the river flows only during 

 one or two days in the year, or is perennial with occasional 

 floods, the nature of the action is the same, and there is no 

 difference in the roundness of the stones. 



I had the good fortune once to witness an example of 

 this. It was in the island of Tenerife, in October 1883. It 

 was said that there had been no rain for six 'months, and 

 certainly all the beds of the streams were perfectly dry. 

 During the forenoon clouds collected, and about mid-day 

 there was a thunderstorm with a violent and prolonged deluge 

 of rain. After the rain had been pouring for about half an 

 hour, a strange rattling sound was heard, which every moment 

 grew louder, without it being possible to say what caused it. 

 At length it explained itself by the bed of the stream in front 

 of the anchorage of the ship in which I was, suddenly filling 

 with brown muddy water, descending with great velocity to 

 the sea and charged with vast quantities of stones, sand and 

 mud. The rattling noise was produced by these stones 

 and rocks being driven violently over the rocky bed and 

 against each other by the current, against which nothing 

 could stand. Naturally all the other river-beds in the island 

 fared alike. Their accumulations were washed away into the 

 sea likewise. The rocks of Tenerife are volcanic and produce 

 in weathering, besides kaolin, hydrated oxide of iron and 

 other ochreous substances, which have a reddish colour. The 

 consequence was that for nearly a week the island was sur- 

 rounded by a fringe of red water. The quantity of rain which 

 fell was so great that when it reached the sea it floated on the 

 top and retained in suspension the fine ochreous mud, which 

 would have been precipitated by mixture with the sea-water 

 had the supply of fresh-water been less abundant. 



A still more remarkable instance of this kind is related 

 by the Prince of Monaco. At the end of August, 1901, he 



