2oG EEBATIO BOULDEES. [CHAP. xi. 



same hemisphere) less than 2 from orchideous parasites, and within 

 a single degree of tree-ferns ! 



These facts are of high geological interest with respect to the 

 climate of the northern hemisphere at the period when boulders 

 were transported. I will not here detail how simply the theory of 

 icebergs being charged with fragments of rock, explains the origin 

 and position of the gigantic boulders of eastern Tierra del Fuego, 

 on the high plain of Santa Cruz, and on the island of Chiloe. In 

 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 unstratified forma- 

 tion 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 

 transported on them. Few geologists now doubt that those erratic 

 boulders which lie near lofty mountains have been pushed forward 

 by the glaciers themselves, and that those distant from mountains, 

 and embedded in subaqueous deposits, have been conveyed thither 

 either on icebergs or frozen in coast-ice. The connection between 

 the transported of boulders and the presence of ice in some form, 

 is strikingly shown by their geographical distribution over the 

 earth. In South America they arc 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 2 from the 

 northern pole ; but in Europe to not more than 40 of latitude, 

 measxired from the same point. On the other hand, in the intertro- 

 pical parts of America, Asia, and Africa, they have never been 

 observed; nor at the Cape of Good Hope, nor in Australia.! 



On the Climate and Productions of the Antarctic Islands. Con- 

 idering the rankness of the vegetation in Tierra del Fuego, and 

 on the coast northward of it, the condition of the islands south 

 and south-west of America is truly surprising. Sandwich Land, 

 in the latitude of the north part of Scotland, was found by Cook, 

 during the hottest month of the year, "covered many fathoms 

 thick with everlasting snow ;" and there seems to be scarcely any 



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



t I have given details (the first, I believe, publisher!) 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 erratic boulders in certain hot 

 countries, are due to erroneous observations : several statements there 

 given I have since found confirmed Ly various authors. 



