LAKE TERRACES. 61 



for these moraine terraces. Without some new term they cannot be referred to, 

 without much circumlocution. In my Eeports on the Geology of Massachusetts, 

 and in a paper on the subject, in the first volume of the Transactions of the Ame- 

 rican Association of Geologists and Naturalists, I called them, in the first work, 

 Diluvial Elevations and Depressions ; and in the other, Iceberg Moraines, but these 

 terms are quite unsatisfactory; and after having ascertained that these objects are 

 connected with, and frequently form a part of, one of the higher terraces, I have 

 named them, merely on the ground of some external resemblances, Moraine Ter- 

 races, which I shall use only until I can find a better term. 



I have not gone into minute details respecting these curious forms of modified 

 drift, because they are given in the works above referred to, and in my Elementary 

 Geology. By recurring to those details, the reasons will be obvious why we can- 

 not explain the phenomena by water alone, nor by ice alone. Their conjoint 

 agency, it seems to me, may do it. 



I ought to add, perhaps, that I have sometimes seen appearances in the bottom 

 of an old river bed, somewhat analogous to the moraine terraces. As such a bed 

 was being filled, when beneath the waters, with sand and gravel, spots were left 

 here and there, several feet deep, which were not filled for want of materials, or 

 from the direction of the currents. But I cannot believe that depressions so deep 

 and numerous, and separated by ridges so narrow and steep, as some of the 

 moraine terraces exhibit, could be the result of mere currents of water. 



28. As to lake terraces I can say but little with much confidence. I cannot 

 doubt, however, that those around most of the small and narrow lakes, such as 

 those of New York and of Switzerland, fall into the same category as the river 

 terraces, while yet the water was high enough to form chains of small lakes. For 

 the drainage of the modern lakes appears to have been going on in the same man- 

 ner as the estuaries, that become ultimately converted into rivers. Such seemed 

 to me to be the case with Lake Zurich and Leman ; and such, I am told, is the fact 

 in respect to the smaller lakes of New York, so that they do not seem to require us 

 to call in any new principle besides those already applied to river terraces. 



As to the larger lakes, I have had no opportunity to examine any of them, save 

 the one called the Bidge Boad, of Ontario, which has more the appearance of a 

 beach, or rather a submarine ridge, than a terrace. Professor Agassiz describes 

 those around Lake Superior, as varying very much in number in different places, 

 "six, and rising from the height of a few feet, to several hundred. He says, that 

 ten, even fifteen such terraces may be distinguished on one spot, forming, as 

 it were, the steps of a gigantic amphitheatre." He distinguishes between these 

 lake terraces and the delta terraces, at the mouths of rivers, which he also 

 describes : and he states also, that the lake terraces "present everywhere undoubted 

 evidence, that they were formed by the waters of the lake itself." He supposes 

 that the shores of the lake have experienced vertical movements ; first a depression 

 and then a rise, and that "these various terraces mark the successive paroxysms 

 or periods of re-elevation" (p. 104, Lake Superior, &c). He supposes the terraces 

 to have been formed, and of course the last elevation of the land to have taken 

 place, subsequent to the drift period: for he remarks, "It is clear that the formation 



