32 STRATIGRAPHICAL GEOLOGY. 



the unaltered Trenton, Utica, and Lorraine * formations of the St. Lawrence valley. 

 There are numerous minute corrugations in the Huronian strata, to the north-west of 

 the gneissic axis. After i^assing the Huronian, the type of formation is that of the St. 

 Lawrence valley, in distinction from that of the more elevated Atlantic region. 



Upon St. Helen's island, in the St. Lawrence, opposite Montreal, is a deposit of 

 Upper Helderberg rocks. The Trenton has been cut on Mt. Royal by a powerful dike 

 of dolerite, which rises back of the city of Montreal in a picturesque manner. To the 

 north-west of this hill appear in order the Trenton, La Motte, and Chazy limestones, 

 the Calciferous sandrock, and the Potsdam sandstone, all lying nearly horizontally, with 

 slight synclinal and anticlinal curves. The last rock on the section is the Labrador 

 system, cropping out in the best known region of its distribution. It probably ex- 

 tends a considerable distance beneath the fossiliferous limestones, and has been much 

 crumpled by lateral forces, being occasionlly inverted. 



Section III. From Mt. Desert Island^ j\/e., to Boiirg Louis., P. J^. 



This section is 220 miles long, and is represented upon Plate IV. The first i^art is 

 mostly derived from a section from Mt. Desert island to the Canada line, published 

 by myself in the second annual report upon the geology of Maine, in 1862. The other 

 portion is compiled as well as may be from the Canada reports. 



The first rock is a sandstone, at Bar harbor, dipping at an angle of twelve degrees. 

 Ripple marks cover the surface of many layers, and curious cylindrical stems tantalize 

 us by their resemblance to fossils. The formation is probably of Cambrian age. The 

 principal part of the island is composed of protogene, with seams resembling strata. 

 Upon the summit of Green mountain these planes dip 60° N. W. At Eagle pond they 

 stand vertically. The first unmistakable strata appear at the north end of the island, 

 consisting of common and talcose gneisses, dipping from 30° to 45° south-easterly and 

 towards Green mountain. The rocks bear a little resemblance to the Bethlehem group 

 of New Hampshire. The water of Frenchman's bay, and a considerable sand in the 

 south jjart of Trenton, obscure the junction between the gneiss and micaceous schists of 

 Huronian aspect. The dijDS are at first north-westerly, and south-easterly after passing 

 Ellsworth village. A calculation of the thickness of the strata, upon both sides of the 

 basin, shows them to be 13,000 feet in amount. 



Next there succeeds eleven miles' breadth of porphyritic granite. My impression is 

 that the crystals in this granite are larger than is common in New Hampshire, and that 

 their larger axes are not arranged in parallel lines. This band is part of the immensely 



* The names of Lorraine and La Motte on the section are used instead of Hudson river and Black river, 

 because the latter do not stand the needful tests of appropriate definition, or of early suggestion. The true 

 Hudson River rocks are now shown to be much older than the place of these shales, as advocated by Prof. 

 Emmons many years since. It is proper, then, as the view so long upheld by Emmons, in opposition to most 

 geologists, has finally been vindicated, that his name of Lorraine should be used when speaking of the slates 

 above the Utica. La Motte limestone or marble was proposed by C. B. Adams, prior to the use of Black river, 

 in the New York reports. The marble is also much thicker in Isle La Motte in Vermont, than along Black 

 river in New York. 



