The results obtained during the progress of the Maine Scientific Survey in 1861, 1862, have been embodied in a large map, the property of the Legislature. By the permission of the executive officers of that State, the map was exhibited to the Association. Gneissic rocks with granite and patches of schist and limestones, occupy the hilly parts of York, Cumberland, and Oxford Counties. This is the remotest extension of the White Mountain series. The same appear in great amount along the coast, including the area twenty miles back, between Portland and the Penobscot River. Between those gneissic masses commences a mica schist, extending north-easterly into New Brunswick. Where it crosses the Penobscot River, it occupies the area between Medway and Bucksport. At the eastern State line it is narrower, including Orient, Amity, and part of Hodgdon. In Hancock County, a range of granite commences at Mount Desert Island and extends north-easterly, entering New Brunswick with the entire width of the Eastern Schoodic Lakes. Another development of mica schist appears on the south of the granite, followed in the south-east part of Washington County by smaller deposits of flinty slates, the Lower Helderberg, Upper Devonian, and by great masses of trappean rocks.

The northern part of the State is sparsely settled, and it is not everywhere easy to trace out the strata. But it is in this section that the greatest number of fossils are found. A wide formation of clay slate succeeds to the great central belt of mica schist. One like it reappears on the Lower Alleguash waters and the St. John River above the Great Falls. This is also underlaid by the Quebec group along the Canadian border. The northern part of the State, from the distribution of these two groups, would appear to form a great synclinal basin, holding at various parts of its surface a long area of Oriskany sandstone, Cauda-Galli grit, and various fossiliferous Upper Silurian and Devonian strata. The clay slates about Waterville contain fine examples of Nereites and Myrianites. The Port Daniel limestone of Lake Sedgwick has afforded a fine series of trilobites and brachiopods. The surface geology of Maine is remarkably interesting. Examples of local glaciers, and thirty-four "eskers," or "horsebacks," have been described. The chief exports of mineral wealth are granite and lime.