Prof. Nicholson — Valleys of Erosion. 319 



which they are occupied, as compared with those which are in every- 

 way caused by mechanical disturbance of the beds through which 

 they run. The great Silurian series of the State of New York pre- 

 sents an appearance which at first sight seems most anomalous to 

 one who has been accustomed to the Silurian districts of the North 

 of England, the South of Scotland, or Wales. In place of having 

 the beds dipping at high angles, contorted and folded in every man- 

 ner, repeated or abbreviated by faults, the Silurians of New York 

 are found succeeding one another with the utmost regularity, for the 

 most part in a nearly horizontal position, and rarely either flexured 

 or interfered with by dislocations of any magnitude. One result of 

 this state of things is that the rivers, in making their way from the 

 high grounds to the sea, have mostly cut for themselves more or 

 less profound ravines, which are generally pure instances of aqueous 

 erosion ; and which are very similar, on a small scale, to the " canons'' 

 of Colorado and Nevada. One of the most striking instances of 

 these valleys of erosion is to be found in what is known as " Watkins 

 Glen," in Western New York, a now famous resort for lovers of the 

 picturesque. Watkins Glen derives its name from the town of 

 W^atkins, which is situated at the head of Seneca Lake in Schuyler 

 County. The lake — which is about forty miles in length — runs due 

 north and south, and the stream which forms Watkins Glen runs 

 nearly due east and west. The lake itself is a long shallow de- 

 pression scooped out of strata of Devonian age, which strike nearly 

 east and west, and are nearly horizontal, or have a slight and almost 

 imperceptible dip to the south. It follows from this that Seneca 

 Lake runs at right angles to the strike of the beds amongst which 

 it is placed. On the other hand, the lateral streams which flow into 

 Seneca Lake from the east and west run more or less accurately 

 along the strike of the strata through which they cut their way. 

 Watkins Glen is a magnificent example of a ravine which has been 

 entirely formed by the stream which now occupies it, and it is only 

 one of many smaller ravines which intersect the eastern and western 

 shores of Seneca Lake. The stream in summer is very diminutive, 

 but its dimensions are doubtless very considerable when swollen by 

 the melting of the snows in spring. The ravine is about one mile 

 in length, and in this short space the stream falls no less than four 

 hundred feet, its course being an uninterrupted succession of small 

 cascades with intervening rapids. Small as the actual stream is, 

 the dimensions of the ravine are very striking. For a distance of 

 about a mile the stream runs between nearly vertical walls of rock, 

 which vary from one to two hundred feet in height. The breadth 

 of the ravine rarely exceeds forty or fifty feet, and the sides are for 

 the most part nearly parallel from the bottom to the top, showing 

 that the action of the stream has been nearly uniform for a long 

 period. The rocks through which the stream cuts belong to the 

 Portage Group (Upper Devonian), and consist of dark shales and 

 flagstones, which are nearly horizontal or have a slight inclination 

 to the south. That the valley is one of pure erosion admits of no 

 doubt, for the beds can be seen crossing unbroken from one side to 



