[47] Faults in the Triassic Formation near Meriden, Conn. Bulletin of the Mus. Comp. Zoöl. Harvard Univ. vol. xvi. No. 4, p. 82. [48] J. D. Dana, Amer. Jour. Sci. 3d. ser., vol. xv, p. 506. [49] J. D. Dana, Amer. Jour. of Sci. 3d ser. vol. xxv, p 446. [50] J. D. Dana, Amer. Jour. of Sci., 3d ser., vol. xxiii, p. 198. [51] J. D. Dana. Amer. Jour. Sci., 3d ser., vol. xxv, p. 441. _STUDIES FOR STUDENTS._ GEOLOGICAL HISTORY OF THE LAURENTIAN BASIN. The study of the Pleistocene history of the basin drained by the St. Lawrence has been fragmentary and is still far from being complete. There is a lack of agreement in the interpretation of observations already made, due in part to the comparatively limited portion of the field examined even by those who have given the subject most attention, and in part to lack of uniformity in the standards of comparison used. It is with the hope of assisting in reaching more harmonious results that attention is here invited to methods of study. In the present treatment of the subject it may be advantageously subdivided, and the facts and hypotheses relating to each division separately considered. Of the divisions that may be suggested the following seem the most important: 1. Character of the sub-morainal or hard-rock topography in the Laurentian basin. 2. Origin of the basin. 3. Sedimentary deposits. 4. Shore markings left by former water-bodies. 5. Fossils in ancient sediments, shore ridges, terraces, etc. 6. Fauna of the present lakes. 7. Changes in elevations of the land. 8. Former outlets. 9. Probable effects of an ice sheet on drainage. 10. Probable effects of a subsidence which would make the basin an arm of the sea. 1. _Character of the hard-rock topography._ In order to learn the character of the Laurentian basin it is necessary to examine the rock surface beneath the general covering of glacial débris and stratified sediments which partially fill it. To do this, those areas in which rock in place forms the surface require to be mapped and their elevations noted; the records of wells and other excavations which pass through the superficial deposits should also be obtained and the character of the underlying rock ascertained, as far as is practicable. When sufficient data of this nature shall have been recorded, a contour map of the basin can be drawn that will reveal the shape of the depression with which the student has to deal. The depth of the present lakes plus an estimated thickness of clay and morainal material covering their bottoms, will probably furnish the only means of sketching contours over the deeper portions of the basin. Even an approximately accurate map of this character cannot be constructed for a long time to come, but every advance towards it will serve to make the problems to be studied more and more definite.