ERRATIC BOULDERS. 319 



Tierra del Fuego, the greater number of boulders 

 lie on the lines of old sea-channels, now converted 

 into dry valleys by the elevation of the land. They 

 are associated with a great unstratifled formation of 

 mud and sand, containing rounded and angular 

 fragments of all sizes, which has originated* in the 

 repeated ploughing up of the sea-bottom by the 

 stranding of icebergs, and by the matter transport- 

 ed on them. Few geologists now doubt that those 

 eri-atic boulders which lie near lofty mountains 

 have been pushed forward by the glaciers them- 

 selves, and that those distant from mountains, and 

 embedded in subaqueous deposits, have been con- 

 veyed thither either on icebergs, or frozen in coast- 

 ice. The connection between the transportal of 

 boulders and the presence of ice in some form, is 

 strikingly shown by their geographical distribution 

 over the earth. In South America they are not 

 found further than 48° of latitude, measured from 

 the southern pole ; in North America it appears 

 that the limit of their transportal extends to 53|° 

 from the northern pole ; but in Europe to not more 

 than 40*^ degrees of latitude, measured from the 

 same point. On the other hand, in the intertropi- 

 cal parts of America, Asia, and Africa, they have 

 never been observed ; nor at the Cape of Good 

 Hope, nor in Australia.t 



On the Climate and Productions of the Antarctic 

 Islands. — Considering the rankness of the vegeta- 

 tion in Tierra del Fuego, and on the coast north- 

 ward of it, the condition of the islands south and 



* Geological Transactions, vol. vi., p. 415. 



t I have given details (the first, I believe, published) on this 

 subject in the first edition, and in the Appendix to it. I have 

 there shown that the apparent exceptions to the absence of er- 

 ratic boulders in certain hot countries are due to erroneous ob- 

 servations : several statements there given I have since founcl 

 confirmed by various authors. 



