Narrative of the surveying voyages of His Majesty's Ships Adventure and Beagle, Vol. 3 [of 3] · Charles Darwin
FOOTNOTES:
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 Hyderabad, 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 that 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. 55 he says, at Iocalla (a few leagues only from Potosi), “a mass of granite many miles in length, rises in huge weather-beaten rocks:” the whole account is to me quite unintelligible. 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.
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