398 CAMBRIAN AND SILURIAN IN NORTH AMERICA. [XV. 



valley of Lake Champlain. These, moreover, offer such litho- 

 logical resemblances to what was called the gray wacke series of 

 Quebec and Point Levis (which extends thence some hundreds 

 of miles northeastward along the right bank of the St. Law- 

 rence), that the two series were readily confounded, and the 

 whole of the belt of rocks along the southeast side of the 

 St. Lawrence, from the valley of Lake Champlain to Gaspe", 

 was naturally regarded as younger than the limestones of the 

 Trenton group. It was in 1847 that Sir William Logan com- 

 menced his examination of the rocks of this region, and in his 

 Eeport for the next year (1848, page 58) we find him speaking 

 of the continuous outcrop " of recognized rocks of the Hudson 

 Eiver group from Lake Champlain along the south bank of the 

 St. Lawrence to Cape Rosier." In his Report for 1850, these 

 rocks were further noticed as extending from Point Levis 

 southwest to the Richelieu, and northeast to Gaspe (pages 19, 

 32). They were described as consisting, in ascending sequence 

 from the Trenton limestone and the Utica slate, of clay-sktes and 

 limestones, with graptolites and other fossils, followed by con- 

 glomerate-beds supposed to contain Trenton fossils, red and 

 green shales and green sandstones ; the details of the section 

 being derived from the neighborhood of Quebec and Point 

 Levis, and from the rocks first described by Bigsby. As fur- 

 ther evidence with regard to the supposed horizon of these 

 rocks, to which he subsequently (in 1860) gave the name of 

 the Quebec group, we may cite a letter of Sir William Logan, 

 dated November, 1861 (Amer. Jour. Sci. (2), XXXIII. 106), 

 in which he says : "In 1848 and 1849, founding myself upon 

 the apparent superposition in eastern Canada of what we now 

 call the Quebec group, I enunciated the opinion that the whole 

 series belonged to the Hudson River group and its immediately 

 succeeding formation ; a Leptcena very like L. sericea, and an 

 Orthis very like 0. testudinaria, and taken by me to be these 

 species, being then the only fossils found in the Canadian rocks 

 in question. This view supported Professor Hall in placing, 

 as he had already done, the Olenus rocks of New York in the 

 Hudson River group, in accordance with Hisinger's list of 



