54 REVIEWS 



2. That, while the larger part of the augife syenite of the Adirondacks is in such 

 situation with respect to the anorthosite as to render impossible any determinations of 

 relative age, its general character is so uniform throughout that it is exceedingly prob- 

 able that it is all of the same approximate age and consists of intrusions from the 

 same source. 



3. That at their borders these syenites pass over into granites, part of which at 

 least cut the syenite eruptively, and are therefore younger. 



4. That the syenite grades into granite on the one hand, and into gabbro diorite 

 on the other, and apparently into anorthosite as well. 



5. That the three together, anorthosite, syenite, and granite, form a great eruptive 

 complex in the heart of the Adirondack region, and that all are younger than the (in 

 part at least) sedimentary Grenville rocks. 



H. P. Gushing. " Pre-Cambrian Outlier at Little Falls, Herkimer Co., N. 

 Y." Nineteenth Annual Report of State Geologist for 1900, published 

 \w Fifty-third Annual Report of New York State Museum, 1900. pp. 



r83-95- 



Gushing describes a pre-Cambrian outlier at Little P'alls, in Herkimer county, N. 

 Y., and points of difference with the syenite of the Adirondacks. 



A. W. G. Wilson. "The Laurentian Peneplain." Journal of Geology, 



Vol. XI (1903), pp. 615-69. 



Wilson describes the Laurentian peneplain of the great pre-Cambrian shield of 

 Canada and adjacent portions of the United States. 'J'he peneplain is an ancient 

 one, which has undergone differential elevation, has been denuded, and subsequently 

 slightly incised around the uplifted margin. At several places on the margin, as 

 exposed today, the dissection may be regarded as submature. The date of the major 

 development of the peneplain is not determined, but may be pre-Ordovician or Creta- 

 ceous. Around the southern margin between Montreal and Winnipeg there are 

 traces of a peneplain (or probably more than one) of still earlier date, upon which pale- 

 ozoic sediments were laid down, and which has been uncovered by processes of degra- 

 dation and denundation since the differential uplift of the latest peneplain. 



S. Weidman. "The Pre-Potsdam Peneplain of the Pre-Cambrian of North- 

 Central Wisconsin." Journal OF Geology, Vol. XI (1903), pp. 289-313. 

 Weidman describes a pre-Potsdam peneplain of the pre-Cambrian of north-cen- 

 tral Wisconsin and shows the same to slope gradually to the south, where it is covered 

 by Paleozoic sediments. Several monadnocks stand above the pre-Potsdam peneplain. 

 Extensive clay deposits near the contact of the Paleozoic and the pre-Cambrian are 

 believed to have developed during the pre-Potsdam base-leveling. 



Comment. — The peneplain described by Weidman is perhaps to be correlated 

 with the pre-Paleozoic peneplain described by Wilson as appearing about the periphery 

 of the great pre-Cambrian area of Canada, with a slope inclined to the great pene- 

 plain of the pre-Cambrian interior. It is of interest also to note that evidence of pre- 

 Cambrian base-leveling has been described by Crosby near Manitou, Col., and that 

 Crosby has called attention to the widespread occurrence of such a plain in North 

 America.' 



'W. O. Crosby, " Archaean Cambrian Contact Near Manitou, Col." Bulletin Geo- 

 logical Society of America, Vol. X (1899), pp. 141-64. 



