516 Notices of Memoirs — Prof. Adams — Laurentian Rocks. 



of wood. Some of the unios do not now live in Canadian waters, 

 but are found in the Mississippi ; and several species of trees now 

 belonging to the States to the south occur with them, indicating 

 a climate decidedly warmer than the present. Above this come 

 stratified clay and sand, with a caribou horn and remains of insects 

 and plants belonging to a colder climate than the present. This 

 set of clays and sands is best shown at Scarborough, where the 

 series rises 14.8 feet above Lake Ontario, and contains many species 

 of extinct beetles, as well as shells of mollusca, mosses, and wood 

 of hardy trees. 



A complicated middle till overlies these beds, which were deeply 

 eroded before the advance of the ice. Another less important fossil- 

 bearing interglacial bed occurs above the middle till at elevations 

 up to 240 feet above the lake, and is followed by a third till. 

 Great changes in the level of the water occurred in connection 

 with these climatic changes, the lake being much lower than at 

 present before the first glacial advance and after the first inter- 

 glacial time. During the deposition of the middle till, and also 

 while the last sheet of till was being deposited, the water stood 

 from 250 to 300 feet above the present level of the lake, which 

 stands 247 feet above the sea. The retreat of the last ice-sheet 

 was followed by the Iroquois episode, leaving a well-marked 

 elevated beach. The length of time required for the first inter- 

 glacial period is probably to be estimated at thousands of years ; 

 and during this time, at the beginning of which the climate 

 was very warm, the ice-sheet of the Laurentide glacier must have 

 completely disappeared. The correlation of the series of events 

 described with those of the drift of the United States and of Europe 

 is difficult, but probably the chief interglacial period corresponds 

 to Jas. Geikie's Neudeckian, or the interval between the lowan 

 and Wisconsin glacial advances. 



IV. — On the Structure and Origin of certain Eocks of the 

 Laurentian System. By Frank D. Adams, Ph.D., F.R.S.C, 

 McGill University, Montreal. 



THE paper presents the results of recent and somewhat extended 

 studies of several areas of the Laurentian of Canada, and deals 

 more particularly with the origin of certain members of this system 

 as indicated by their structure or composition. While it is impossible 

 in the present state of our knowledge to arrive at any definite 

 conclusions concerning the origin of many, or perhaps even of the 

 majority, of the rocks composing the Laurentian, the origin of 

 certain members of the system can be determined. Some of these, 

 although now possessing a more or less distinct and even highly 

 pronounced foliation or stratiform appearance, can be proved to be 

 igneous or intrusive rocks, while it can be shown that others are of 

 aqueous origin. 



To the former class belong the anorthosites and many of the 

 orthoclase gneisses. These rocks, although frequently distinctly 

 foliated, can in many places be traced into perfectly massive varieties, 

 and form great intrusions, interrupting and cutting off the older 



