1 855.] on Trains of Erratic Blocks in Massachusetts. 97 



of mankind live now as they have always lived, near the equator, or 

 in countries not more than 25 degrees distant from it, they can 

 never behold ice or snow. We may imagine, therefore, a nation to 

 liave made considerable progress in science without knowing any- 

 thing of the causes appealed to in this discourse. If such a people 

 were told by travellers of the geological appearances above 

 described, how great would be their perplexity ! They might at 

 first ascribe the transport of erratics to floods of extraordinary 

 violence, but they would scarcely be able to hazard a reasonable 

 conjecture in regard to the coincidence between the direction of 

 glacial furrows and that of the trains of erratics. A stone, not 

 held fast by ice, but merely pushed along in mud, could not scoop 

 out a long rectilinear furrow, one inch, or sometimes a foot deep, 

 in a hard rock. Still more mysterious would be the discovery 

 of a connection between the former migration southwards of an 

 arctic fauna, and the conveyance of large erratics to the same 

 regions. If the glacial hypothesis afforded no more than a plausi- 

 ble explanation of the association of so many distinct and indepen- 

 dent classes of phenomena, it would deserve greater favour than 

 has been shown to it by some modern geologists. The inclination 

 evinced by many to introduce catastrophic action, as peculiarly 

 applicable to the case of drift, arises in a great degree from the 

 absence of stratification in drift. The usual geological proof of 

 successive accumulation, and of the lapse of time, is here want- 

 ing ; hence the sudden uplifting and sinking of land, the dis- 

 placement of the sea, and the raising of gigantic waves of 

 translation, rolling over continents at the rate of fifty miles an hour, 

 accompanied by rapid gyrations of the marine fluid, have been 

 imagined. The rate of movement, suggested by the glacial hypo- 

 thesis, is singularly opposed to these views. Blocks carried by 

 glaciers travel for centuries at an average rate of less than an inch 

 per hour, and those borne along by floating ice float a mile or a 

 mile and a half an hour. The observer of icebergs can seldom tell 

 whether their course be north or south, east or west. In like man- 

 ner the submergence and re-emergence of land will best account for 

 the appearances above described, if the movement were slow, as now 

 in Greenland and Scandinavia ; in other words, if it be such as 

 would be insensible to any human inhabitant. Yet the power of 

 the machinery appealed to in both cases is equally vast ; for it must 

 be capable of uplifting and depressing continents, and removing 

 from place to place the great volume of superficial materials found 

 in the drift. The real difference of opinion consists in the amount 

 of time during which the force is supposed to have been developed. 



[C. L.] 



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