1870.] 279 [Shaler. 



at Watertown, in a nearly north course of about a quarter of a mile. 

 For the first two hundred yards of its course, its form is quite remark- 

 able, separating it distinctly from the usual ridges of drift material 

 found in this vicinity. It stands on the alluvial plain of the river like 

 a fragment of a great dam, having a height of about twenty five feet, 

 and a breadth of about one hundred. Following it in its northward 

 course, it gradually becomes less distinct as it comes out of the valley 

 of the river, and little by little fades away. Having been plowed 

 over for nearly two centuries, the northward extremity is no longer 

 clearly marked. 



There are three sections visible in the moraine ; one at its northern 

 extremity, another where a water gap traverses the rampart, another 

 where it is cut by the Watertown Railroad. At each point it is evi- 

 dent that the structure of the mass is that of all true moraines: stones 

 of varied dimensions mingled together with a certain admixture of 

 clay and sand make up the mass, which seems entirely without strati- 

 fication. The general character of the material differs markedly from 

 that of the drift found on Somerville Hill, or in any other of the 

 massive glacial deposits. It is much less compact, the fragments are 

 more angular and of much less varied mineral composition ; fragments 

 of slate rock greatly preponderate in the mass, being much more nu- 

 merous than in any of the other drift deposits of this vicinity, unless 

 it be in the other moraines of the same valley. 



The relation of this rampart to the other beds of the valley, seems 

 to indicate that it must have been formed after the close of the first 

 division of the ice time, later indeed than the commencement of the 

 reelevation of the land. The ice stream does not seem to have risen 

 to a great height on the sides of the valley, as the moraine does not 

 extend more than fifty feet above the high water mark. 



On the south side of the river there is visible what seems to have 

 been a continuation of this moraine, or possibly a lateral moraine 

 formed at the same time. I am not quite sure, however, of its real 

 relations to that just described. 



It is with much hesitation that I pronounce upon the character of 

 this ridge of drift. I can say, however, that outside of the Alps I 

 have never seen anything as clearly referable to the forces which 

 build terminal moraines, and that in Switzerland no geologist would 

 hesitate an instant to refer it to this group of glacial deposits. 



