392 NOTICES OF NEW BOOKS. 



the sandstones of this period many ripple marks are found, and the 

 surface of the slabs is frequently covered with fucoidal impres- 

 sions ; but fossils appear to be rare. 



It is chiefly with regard to strata of the carboniferous period 

 that the investigations of Mr. Lyell in North American palaeozoic 

 geology must be considered important. The coal fields of the 

 United States and the British possessions in Canada are beyond 

 all comparison the most extensive and the most valuable of any at 

 present known in the world ; and the geological position of these 

 deposits of vegetable matter, as well as the conditions under which 

 they occur, are matters of very considerable importance to the 

 future interests of the continent of America. 



The great coal fields of the United States are the Appalachian, 

 the Illinois, and the Michigan : those of the Canadas are on the 

 eastern extremity of the colony, and occupy a great space in New 

 Brunswick, Prince Edwards Island, Cape Breton, &c. A large 

 proportion of the coal is anthracitic. It is not easy to do justice 

 to these formations by the hasty sketch to which our limits neces- 

 sarily confine us in this place ; but some idea may be formed of 

 their extent, when it is stated that the Appalachian coal fields ex- 

 tend for a distance of 720 miles from north-east to south-west 

 with a width in some places amounting to 180 miles * ; that the 

 Illinois basin is not much inferior in dimensions to the whole of 

 England ; that the Michigan coal fields and the coal fields of 

 Canada are also of very considerable dimensions ; and that the 

 thickness of the seams of fossil vegetable matter in some instances 

 exceeds even that of the Staffordshire coal, amounting at the 

 Lehigh summit mine (where the usually intervening shales and 

 grit have thinned out) to one mass of fifty feet without any greater 

 interpolated matter than two thin layers of clay. In some places 

 this vast bed is quarried in the open air ; but in others, where the 

 coal is accessible to a degree scarcely to be imagined by strangers 

 to the conditions of the country, the time has not yet arrived when 

 the value of it as fuel is appreciated. (See vol. ii. p. 26, 27.) 



One of the most remarkable facts, geologically, with reference 

 to the carboniferous deposits of North America, is the great 

 abundance and excellence of the anthracitic coal, met with more 

 especially in the Alleghanies ; but as Mr. Ly ell's views and con- 

 clusions on this subject were communicated to the Geological 

 Society shortly after his return to England, and have since been 

 published in this Journal (see ante, p. 199.), it is not necessary 

 here to dwell upon or recur to them ; we rather prefer directing the 

 attention of the reader to the coal fields of Nova Scotia as being a 

 district in which our author has made most important additions to 

 our knowledge of palaeozoic geology, and as the subject offering 

 the greatest amount of new matter for consideration. 



The carboniferous group of formations, as developed in Nova 

 Scotia, may be conveniently divided into three series, namely : — 



* Its superficial area is calculated at 63,000 miles. 



