142 SURFACE GEOLOGY. 



Since that time the river has been changing its course, and the overlying 

 fine silt has been deposited from its floods upon the deserted river-bed. 



Modified Drift along Saco River and in the Basin of Ossipee 



Lake. 



The areas which are occupied by modified drift in this part of the state 

 are delineated on the general geological map in the atlas ; and a special 

 map on Plate VI shows the extensive plains about Ossipee lake.* 



The south-eastern part of the White Mountain district is drained by 

 the Saco, which has its farthest sources in Saco pond and Mt. Washing- 

 ton river. The water-shed at the Crawford house, which divides this 

 from the Lower Amnion oosuc river, is formed by a deposit of very coarse 

 modified drift (p. 62), which was swept down into this mountain pass in 

 the Champlain period. Its height is 1,900 feet above the sea; and Saco 

 pond, which fills a depression in this deposit, is 20 feet lower. The small 

 stream which issues from this pond passes through the White Mountain 

 Notch, falling 600 feet in the first three miles, and nearly as much more 

 in the next nine miles. Along this distance it flows between lofty moun- 

 tains, whose sides are often precipitous walls of rock. A fine view of 

 this part of its valley is afforded from the top of Mt. Willard. Far above 

 rise the rugged heights of Webster and Willey, almost vertical in their 

 upper part, but below bending in graceful, regular curves, composed of 

 materials which have fallen from each side and form an apparently 

 smoothed hollow for the highway and river. The principal superficial 

 deposits along this steep portion of the river are such rocky debris which 

 has crumbled from the mountains, or the equally coarse unstratified till. 

 In the bed of the stream these materials have become water-worn, but 

 only limited deposits of gravel and sand are found. It is worthy of note, 

 that in constructing the Portland & Ogdensburg Railroad the excavations 

 yielded an abundance of sandy gravel suitable for ballast. To make a 

 gradual ascent, this road is built along the side of the valley; and some 

 of these excavations were two or three hundred feet above the stream. 



At the west line of Bartlett the Saco is 745 feet above the sea. In the 

 next eight miles to the mouth of Ellis river, it descends about 30 feet to 



* This river system is described in Vol. I, on pp. 301, 311, and 312. 



