In 1877 the writer published in the second volume of the Geology of New Hampshire a general description of the rocks of the Ammonoosuc district, the region extending from Woodsville to Lancaster, where the Connecticut river bends conspicuously to the west and has apparently annexed a part of Vermont to New Hampshire. The Connecticut has cut across a mountainous range in what is known as the Fifteen Miles falls, causing the drainage of the upper part of the state to unite with that of the Passumpsic river. On some other occasion I hope to revive an old theory, advocating the former drainage of the upper Connecticut through the lower Ammonoosuc to join the Passumpsic waters at Woodsville (Wells river, Vermont). Between these two valleys and the field of our inquiry there happens to be a fine development of Paleozoic strata with fossils, so that it is possible to know . . .