GEOLOGY OF THE CAMPSIE HILLS'. 41 



quently be seen in the operation of starch-drying, 

 and in some of the preparations for pottery. 



Upon the large scale, this operation of nature 

 is to be seen to the greatest advantage in warm 

 climates, where evaporation is strong and rapid ; 

 one example of which, I shall here beg leave to 

 describe, it having struck me as being a remark- 

 ably good and explanatory specimen of this phe- 

 nomenon. The notes which I took upon the spot 

 where this specimen occurred, are now before 

 me. 



In the Mediterranean, on the coast of Africa, 

 this example fell under my observation some years 

 ago. In the near vicinity of a considerable rivu- 

 ' let, deeply imbedded in a soft soil, there had ex- 

 isted a piece of w^ater of considerable expanse, 

 on a level of about twenty feet above the stream 

 of this rivulet ; one of the windings of this stream 

 had undermined, and had carried off a great part 

 of a rising ground that had served to imbank 

 upon one side this former lake ; which bank, 

 vv^hen broken down, had given drainage to it, and 

 had laid open its deposited soil to a considerable 

 depth. Upon this broken down side, the soil of 

 the former lake displayed a beautiful arrangement 

 of columnar forms. These were in length about 

 eighteen feet, and were from a foot and a half 

 to three feet in diameter, but, as to their magni- 

 tudes and forms, they varied much from each 



