Reviews — Dr. T. Sterry Stint's Penmylvanian Report. 519 



direction of the glacial strife so fully described in vol. iii. (chapters 

 1 and 2) ; besides a geological map in six sheets, clearly illustrating 

 the description of the stratified and other rocks given in the second 

 volume. This map, while indicating the results of the labours of 

 the State Geologist and his colleagues during their explorations, 

 will, besides its local interest, facilitate the comparison of the geo- 

 logical features of New Hampshire with those of the surrounding 

 territories. J. M. 



II. — Special Eeport on the Trap-dykes and Azoic Rocks of 

 South-eastern Pennsylvania. By T. Sterry Hunt. Part I. 

 Historical Introduction. (Harrisburg, 1878.) 



THIS work forms the first portion of a special report by Dr. Hunt 

 on the Azoic Rocks, Trap-dykes, and Iron Ores of Pennsylvania. 

 It contains an Introduction to the Geology of South-eastern Pennsyl- 

 vania, an account of the Cambrian Rocks of Europe and America, 

 and three chapters (II. III. V.) on American Pre- Silurian Geology, 

 which comprise an historical and critical review of the progress of 

 our knowledge bearing on the older rocks of North America, during 

 the last sixty years, — from the publication of Maclure's map in 

 1817, until the present time. It would be impossible to condense 

 satisfactorily, in this brief notice, the opinions and descriptions of 

 the various writers cited throughout the work, which Dr. Hunt has 

 himself so concisely and clearly treated, as well as interspersed 

 many suggestive remarks, on the characters, origin, and sequence of 

 the Azoic rocks, considered to be of Pre-Palaeozoic age, and which 

 are also fully noticed in his Chemical and Geological Essays. As, 

 however, the recent researches of Dr. Hicks and others in this 

 country (see Geol. Mag. ante, p. 433) have shown certain crystal- 

 line rocks to be of Pre-Cambrian age, it may be useful to give the 

 results of the recent studies of Dr. Sterry Hunt on the older rocks 

 of Eastern North America, including the Lake Superior region. 

 These terranes are, in descending order, as follows : — 



8. Siluro-Cambrian. — The Upper Cambrian of Sedgwick, part of the Lower 

 Silurian of Murchison, and of the Matinal of Rogers. 



7. Cambrian.— The Lower and Middle Cambrian of Sedgwick, the Lower and 

 Upper Cambrian of Hicks ; the Upper Taconic of Emmons, and the Quebec group 

 of Logan ; the Primordial, and part of the Lower Silurian of Murchison. 



6. Keeweenian. — The Copper-bearing series of Lake Superior, found in the 

 same geological interval as the Taconian, but not identified with it. 



5. Taconian. — The Lower Taconic of Emmons, including a part of the Primal, 

 Auroral, and Matinal divisions of Rogers, and constituting, with the Montalban, 

 what was once called Terranovan by the writer. 



4. Montalban.— The White Mountain or Mica-schist series. 



3. Huronian.— The Green Mountain series, or altered Quebec group of Logan. 



2. Norian. — The Labradorian, or Upper Laurentian of Logan. 



1. Laurentian.— A lower division, the Ottawa Gneiss, and an upper division, 

 the Grenville series, between which is a supposed unconformity. These two con- 

 stitute the Lower Laurentian of Logan. 



With regard to the five lower terranes, they have, notwithstanding 

 their differences, certain lithological resemblances with each other. 

 "All of them include quartzites, and crystalline limestones, in 



