The area herein described is that part of New York State lying south of Lake Ontario, and west of longitude 76°. The dimensions of the area are, approximately, 95 miles north and south and 155 miles east and west, or nearly 15,000 square miles. The rocks are shales, sandstones, and limestones of the Upper Silurian and Devonian systems. The strike is nearly east and west, with a southward dip averaging perhaps 50 feet to the mile.

In order that progress may be made in any branch of geology, it is necessary, not only that the faculties of observation and inductive reasoning should be employed, but a proper use should be made of the imagination. By this means new lines of research are laid out. The theory we set ourselves to prove may eventually prove to be wrong, but it often happens that the pursuit of a false theory brings one as near the truth as the following up of a true one. It is in this spirit I wish you to regard the problems and speculations to which I now invite your attention.

Dr. Daniel Russouw Kannemeyer sent me a photograph of a dental plate in April, 1897, to which was appended the remark—“I conclude it to be Ceratodus, and its bones are said to be lying at Kraai Fontein. I have sent the man who found it to search for and fix the locality.” The search was not successful; and since then the rinderpest has prevented any attempt to reach, the locality, which is geologically at the top of the Karoo beds above the Coal of the Indwe district of Cape Colony, in strata which yield Zanclodont reptiles in other localities.

In calculating the throw of a fault, it is usual to assume that the whole of the displacement due to the fault has been produced by a vertical motion—i.e. by a motion in a vertical plane at right angles to the direction or strike of the fault—and that there has been no such thing as a lateral movement of one face of the fault upon the other.

In several parts of South Africa, thick sedimentary and unfossiliferous deposits are found resting on gneisses or highly altered rocks. They are well developed in the Southern Transvaal around the towns of Johannesburg and Potchefstroom; in the Northern Transvaal in the districts of Lydenburg and De Kaap, and possibly Zoutspansberg; in Matebeleland, Bechuanaland. Griqualand West, Damaraland, and Zululand.