G. II. Stone — Glacial Sediments of Maine. 129 



abruptly in gravel or sand, and the marine clay which usually 

 overlies them is plainly a later deposit, not contemporaneous. 

 They are mostly found below 230 feet. They vary much in 

 size up to half a mile in breadth and two or three miles in 

 length. The coarseness of the sediment proves that the waters 

 of the glacial rivers were never so far stopped as to permit 

 them to drop the finer detritus, as would have happened if a 

 glacial stream poured into an open body of water of the size of 

 the whole plain. The best interpretation of the facts is that a 

 glacial stream poured into a pool or lake within the ice. This 

 lake was not large enough to stop the stream sufficiently to 

 cause it to deposit its clay but did check the current somewhat 

 so as to make it drop the coarser sediment. Thus it happened 

 that the central part of the pool was filled with sand and 

 gravel while at the same time the pool enlarged by melting 

 and erosion of the adjacent ice. Thus after a time the real 

 pool consisted of a narrow strip of water situated between the 

 central bar of gravel and the surrounding ice. In this narrow 

 passage the velocity of the water was not sufficiently lost to 

 permit the deposition of the finer sand and the clay, nor were 

 any large kettle-holes made. The stratification of such portions 

 of these broad plains as I have been able to examine is irregu- 

 larly quaquaversal. 



In the northeastern part of Monmouth are three deposits 

 each consisting of two elongated-semicircular plains of coarse 

 sediment separated by a central ravine. The plains are situ- 

 ated on hills where no stream can have existed to account for 

 the ravines by ordinary stream erosion. My interpretation is 

 that a swift glacial river flowed into one side of a lake con- 

 tained within ice walls and out at the other side without losing 

 much of its velocity. The ravines mark the channel of the 

 glacial river, while the lateral gravel plains collected in the 

 still water on each side of the swift current. These plains are 

 one-fourth of a mile in diameter, one of them somewhat more. 



We thus find several transition forms between the kame 

 proper and the complete delta, i. e., the plain that was formed 

 in a body of water sufficiently large, as compared with the size 

 of the glacial river, to completely check the flow of the incom- 

 ing water. Some of these intermediate forms perhaps deserve 

 recognition in our classification. 



6. The discontinuous kame systems. — These consist of 

 deposits of glacial sediments, arranged in linear series, and sep- 

 arated by intervals varying in length from a few feet up to 

 two or three miles. When mapped, the linear arrangement is 

 very obvious. The gravel takes the form of domes, cones and 

 short ridges, often of considerable breadth so as to be plain - 

 like. These massive ridges or plains are found here and there 



Am. Jotjr. Sci. — Third Series, Vol. XL, No. 236. — August, 1890. 

 9 



