316 



POSITION. 



small icebergs, or the freezing of water, that tends to throw up the edges of the islands only, and particu- 

 larly the western edges. 



Our notes also state that upon these eastern islands there are numerous small folds in the strata. Single 

 layers, a few inches thick, will form a loop, and the loop itself be interstratified with the other layers ; in 

 other words, they are miniature inverted anticlinals, so numerous as to arrest the attention, and that not 

 merely upon a single island. They are not far from the strike of the Highgate anticlinal. We do not sup- 

 pose that their looped strata necessarily imply more than that there has been a considerable pressure exerted 

 upon these strata, and that force acted probably at the 

 same time that the neighboring anticlinal was folded 

 up. 



Fig. 233 shows the position of the strata upon 

 Welden's Island, near St. Albans. The eastern side 



of the island, where the sketch was taken, is about Section of Weideu's island. 



twenty five feet high. The cliff is found upon every 



side except the north, where it slopes gradually to the level of the lake, the slope being covered by Champlain 

 clay. Numerous large bowlders of Laurentian rocks from Canada are strewn at the base of the cliffs. The 

 section is about half a mile in length. 



FIG. 233. 



Champlain Cloyx. 



Section at Rich's Quarry, Swanton. 



Explanation of Fig. 234. 

 a Hudson River shales. 



b Swanton marble, or dove-colored limestone, out of which the stone quarried at Rich's quarry is obtained. 

 c Clay slate, run east of Rich's quarry, near the Vt. and Canada Railroad. Supposed to be of the Hudson R. Group. 

 A Variegated dolomites of the Red Sandrock Series. 

 e Georgia slate. 



Fig. 234 in connection with Figs. 228, 229 and the Geological Map, Plate I, illustrate a 

 development of clay slates in the northern part of the Hudson River Group, which has 

 not been observed south of St. Albans, namely : there is quite a thickness of clay 

 slates, c, in Fig. 234, in the upper part of the group ; between the upper limestone, b, 

 which is elsewhere at the top of the series, and the red sandrock series, d. Prof. Eminons 

 regards this slate, c, as of the same age with the Georgia slate, e, and supposes that the 

 red sandrock, d, is not interstratified with the slates, but rests upon them unconformably. 

 And he regards both the slates as Taconic slate. 



There is a question of great importance concerning the stratigraphical relations of this 

 upper band of clay slates to the red sandrock series which we cannot answer satisfactorily 

 to ourselves, without further investigation. With this question is also involved the age 

 of the slates, whether they are older or newer than the red sandrock series, and whether 

 the slates west of the red sandrock are the same with the Georgia slates east of the red 

 sandrock. The two geologists who have examined the positions of these rocks in north- 

 ern Vermont or Canada Sir W. E. Logan and Prof. Emmons agree in regarding the 

 red sandrock series as of lower Silurian age (near the calciferous sandrock), and also agree 

 in considering the Georgia slate as older than the red sandrock. Logan calls all the 

 slates west of the red sandrock Hudson River slates, while Emmons regards a part of 

 them those nearest the red sandrock as Taconic. Consequently they differ in their 



