290 TiERRA DEL FUEGO. June, 1834. 



very great weight in support of the mass of positive evidence 

 which Mr. Lyell* has brought to bear upon the question. 



and the greater number of even the same coloured variety, as the granitic 

 rock, on which they rest, the case need not be considered. Secondly, in a 

 late number of the Madras Journal, Dr. Benza has described some erratic 

 blocks lying on a plain between the Neilgherries (lat. 12° N.) and Madras. 

 He states that the foundation-rock of the country is gneiss, " while the 

 granite clusters are more elevated, and affect either a prismatic form, or 

 are piled up one on the other, like logging stones." Dr. Benza had the 

 kindness to inform me that these masses are very large, and that several 

 are piled one upon the other. Again, Brongniart says (Tableau de 

 Terrains, p. 83), " On cite aussi dans I'lnde, au pays d'Hyderabad 

 (lat. 17° N.), des blocs cnormes de granite, amonceles les uns sur les 

 autres" (Deluc neveu). Every one must draw his own conclusions from 

 these accounts, regarding the probability of erratic blocks being heaped 

 up, one upon the other, like logging stones. The same doubt likewise 

 partly applies to the Macao case. With respect to the boulders of Hydera- 

 bad, Dr. T. Christie has distinctly stated (Edin. New Phil. Jour., Oct. 1828, 

 p. 102), that they are in situ, and has explained their origin. For my 

 own part, I cannot forget ihat whole granitic hills at the Cape of 

 Good Hope, which, from weathering, have assumed a boulder-like form, 

 were once described as transported masses. The two next cases do not 

 properly come under consideration, for they refer to masses lying in the 

 valleys of lofty mountains. We must not overlook such accidents as 

 bursting of lakes, earthquakes, and the action of former coast-lines. Helms, 

 in his Travels (English translation, p. 45), states he was astonished to 

 find the highest snow-capped mountains near Potosi (20° N.) covered 

 with a stratum of rounded granitic stones. He supposes they must have 

 come from Tucuman, which is several hundred miles distant ; yet at p. 53 

 he says, at localla (a few leagues only from Potosi), "a mass of granite 

 many miles in length, rises in huge weatherbeaten rocks :" the whole 

 account is to me quite uninteUigible. Lastly, M. Gay (Annales des 

 Sciences, 1833) describes granitic boulders within the valley of Cauquenes 

 (lat. 33°-34° S.), in the Cordillera. I visited this place : the boulders and 

 pebbles are not large, and those beyond the mouth of the valley are small. 

 The case did not appear to me nearly so extraordinary as it seems to have 

 struck M. Gay. I cannot agree with his assertion that this rock is not 

 found in that part of the Cordillera : but this is a subject which I shall 

 discuss in a future work. 



J The absence of great embedded fragments in the formations of the 

 secondary epoch, when we know that the climate was of a more tropical 

 character, is a fact of the same kind. 



