The present contribution deals with certain igneous rocks in the townships of Ticonderoga, Crown Point, Moriah, Westport, Essex, Willsborough and Chesterfield, which lie along the western shore of lake Champlain, in Essex county, New York. In them the most important phases of the great igneous body that forms the bulk of the Adirondacks are illustrated, and in many particulars petrographic details are adduced which have not been previously noted from this region. The field work in Moriah and Westport was done with the support and under the direction of Dr F. J. H. Merrill, director of the New York State Museum, and in the other towns, except Chesterfield, with the aid of the trustees of Columbia College, while in Chesterfield and a number of interior townships not mentioned here the writer has had the support and direction of Professor James Hall, state geologist. These results are published with the . . .