GLACIO-AQUEOUS ACTION IN NORTH AMERICA. 201 



with the du-ection of the strise upon the rocks in Andover, which 

 is nearly north and south. The idea of glaciers, however, occur- 

 ing in this almost level region, and removed one hundred and 

 fifty miles from any mountains whence glaciers might have 

 descended, appears to me absurd : and hence the work must 

 have been accomplished by icebergs. 



It might be supposed, perhaps, that these ridges were produced 

 as ridges of sand and gravel sometimes are, along the sea coast 

 and near the shores of lakes, by the action of waves and currents, 

 when the region was under water. But in the first place, they 

 are much steeper and narrower than any such ridges now form- 

 ing. Indeed, we cannot conceive how it is possible for water 

 alone to pile up such ridges. In the second place, no lake or 

 other expansion of water could have existed in this valley, wide 

 enough to allow its waves to produce such an effect ; as in order 

 to do it, they must have moved either from the east or the west, 

 and the ridges are but a short distance from what must have been 

 shores in such a case. Finally, the materials of these ridges were 

 brought mostly from the north ; and waves, or a stream, moving 

 southerly, through a passage not wider than a large river, could 

 not have produced high longitudinal ridges. These difficulties 

 will strike a person more forcibly who examines the spot, than 

 when stated in language. 



I presume that still further careful examination of the region 

 above described, may show other similar ridges, or a continuation 

 of those on the map. Indeed, remnants of them are discoverable 

 further south ; but it was thought best not to represent them. At 

 their northern extremity, a deposit of coarse sand appears to have 

 been subsequently brought in by water, which has covered them 

 up, A mile or two south of their southern extremity, moraines 

 abound, which have not yet been examined with reference to the 

 existence of continued ridges. In company with ]Mr. Gray, I 

 visited South Reading ; where, at the northern extremity of a 

 valley, and a few rods east of the village and a pond, is a very 

 interesting ridge, nearly half a mile long, of the same general 

 character as those in Andover. It is quite serpentine ; and on its 

 east side especially, quite steep. In some places, also, it is higher 

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