GEOLOGY OF THOUSAND ISLANDS. 95 



rock, which in places imperfectly assumes the co- 

 lumnar shape. These columns seem very much 

 shaken, as if ready to fall to pieces ; and the tops 

 of the columns, as well as all corners and protu- 

 berances, are much worn and rounded, as if they 

 had been half made into boulders already. They, 

 no doubt, are so ; for thousands of boulders, quite 

 smooth and rounded, and formed of the same rock, 

 half cover the islands. These are mostly of an av- 

 erage size of about a cubic foot, and very seldom 

 exceed two feet and a half in diameter. They are 

 curiously packed and leveled in some places, as if 

 they had been roughly made into a causeway for 

 walking on by human agency. This singular ap- 

 pearance I conceive to have been given to them by 

 enormous icebergs grazing over and resting on the 

 islands ere yet they became dry land, and acting to 

 the boulders like a roller on a gravel-walk. Among 

 these native boulders I was a little surprised to find 

 a few very round and smooth boulders of red gran- 

 ite, of about one cubic foot downward in size, as 

 there is no granite nearer than the inaccessible 

 peaks of the primitive ridges in the centre of Spitz- 

 bergen, distant forty or fifty miles. There were 

 also some boulders of a hard reddish stone like por- 

 phyry, and some small weather-worn blocks of a 

 very hard white limestone, of a description different 

 from any limestone rock which I have any where 

 seen in situ in Spitzbergen. It seems to me that 

 all these interlopers must have traveled either from 



