March 8, 1894] 



NATURE 



435 



them. The latter system, accordingly, "has no limit 

 downward. It is the oldest system, and surely includes, 

 if such rocks exist, all of the original crust of the earth." 

 The upward limit also is not easily defined, but ''it is 

 frequently easy in the field to say, with a great degree of 

 probability, what rocks are Archxan and what post- 

 Archaean." Thus the former system includes the original 

 Huronian of Logan, which the author inclines to think 

 separable into two divisions, the lower of which comes 

 nearer than the upper to assuming a crystalline character. 

 It also covers the Animikie and the Keweenawan 

 of Irving ; in short, a vast group of rocks which are 

 generally clastic in origin, and seldom more than sub- 

 crystalline in character, in certain of which undoubted 

 traces of life — though very rarely — have been found. The 

 origin of the Archtean system is considered to be a 

 problem yet unsolved. Its rocks are highly crystalline, 

 and if any have been formerly sediments all traces of a 

 clastic origin have been completely lost. It certainly 

 constitutes a complex, probably to no small part of 

 igneous origin, and the author evidently inclines to the 

 view " that this earliest crystalline complex was pro- 

 duced under conditions differing from those of the rocks 

 of any subsequent period. He would employ the term 

 Laurentian in a more restricted sense than that in which 

 it was used by Logan for the gneissoid part of the Archaean, 

 while he dismisses most of the six pre-Cambrian rock 

 systems of the late Sterry Hunt and his school as 

 hypothetical existences to which the atmosphere of the 

 laboratory was more congenial than the air of the 

 field. 



In a subject so difficult as these pre-Cambrian rocks, 

 where so many things are yet unsettled, Prof, van Hise 

 cannot expect to satisfy all readers. Speaking for our- 

 selves, we think he is disposed to attribute too much 

 potency to dynamic metamorphism — an agency which is 

 being rather "boomed" at the present time — and to 

 admit on too slight evidence that in " Silurian, Devonian, 

 and even later times, completely crystalline schists have 

 been produced over large areas"; for in the past this 

 assertion has been so often made, and so often proved to 

 be erroneous, that on the principle, " once bit twice shy," 

 we are disposed to be a little sceptical. But whether 

 we accept or whether we demur to the author's conclu- 

 sion, we gladly welcome his volume as a contribution to 

 the history of the pre-Cambrian rocks which will be in- 

 valuable to students, and is full of sagacious criticism and 

 suggestive remarks. 



The next Correlation Paper (No. 85), written by Mr. I. 

 C. Russell, deals with the Newark system, which occu- 

 pies a series of rather elongated outcrops in the Eastern 

 States, and runs along the shore of the Bay of Fundy. 

 The fragmental rocks of this system, which includes the 

 well-known New Red Sandstone of Connecticut, vary 

 from coarse to fine ; a few thin seams of coal and lime- 

 stone are also present. Dykes and sheets of basalt, &c. 

 occur in almost every area. The system is limited by 

 an unconformity, both above and below, and is not easily 

 correlated precisely with those of Europe, but the rep- 

 tiles, amphibia, and Crustacea correspond generally with 

 those of the Keuper, the fishes with the Alesozoic rather 

 than with the Palzeozoic, and the plants with the Upper 

 Trias or Rhsetic, so that it evidently represents an early 

 portion of Mesozoic time. 



A third Correlation Paper (No. 82), by Mr. C. A. White, 

 deals with the Cretaceous. This system occupies in the 

 interior a very wide zone (the southern half being the less 

 uniform in outline) which extends roughly from latitude 28" 

 to 60". Further north are some outlying patches ; near 

 the Pacific coast is a long string of the same, and in the 

 Southern States east of the Mississippi a crescentic area. 

 The rocks, especially in the Interior Basin, have been 

 affected in many places by great displacements both 

 during and after Cretaceous times, but though over a 



NO. 1 271, VOL. 49] 



large part of this region they have been elevated from 

 about one to five thousand feet above the sea, they 

 generally lie almost horizontally ; these displacements 

 are more frequent in the Lower than in the Upper Cre- 

 taceous. Also much volcanic material was extruded 

 during this period as well as after its close. In the In- 

 terior Basin marine deposits alternate with freshwater, 

 but the latter predominate, showing that the land was 

 more often above than below sea level. 



The Eocene forms the subject of another Correlation 

 Paper {Bulletin No. 83), by Dr. W. B. Clark. The rocks 

 of this period occur in the same regions as the Cretaceous, 

 but occupy much less extensive areas in the western half 

 of the continent, while they are more largely developed 

 in the south-east, extending from the Mexican frontier to 

 New Jersey State. The last, as is well known, are 

 marine, and comparable with the deposits on the other 

 side of the Atlantic, but the correlation of the various 

 groups of the Interior Basin, including the transitional 

 Laramie deposits, is very difficult, probably because the 

 flora and fauna of these inland waters, as they were 

 changing from brackish to fresh, present so few points 

 of comparison with other regions. Still, Dr. Clark's clear 

 summary of the main results of investigation, and of the 

 succession of the strata, will be very helpful to the 

 student. 



The last Bulletin before us (No. 84), by Messrs. W. H. 

 Dall and G. D. Harris, describes the Neocene. This 

 term is supposed to include the Tertiaries other than 

 Eocene. We have not troubled to inquire to whom be- 

 longs the honour of its paternity. If it does not mean 

 New-new, then words respectively more applicable to 

 persons and things are combined. Perhaps the one half 

 was intended to apply to the animals, the other to the 

 rocks ; or perhaps — what is more usual with geologists — 

 nobody troubled himself to think whether the term was 

 sense or nonsense. The memoir, however, is full of 

 valuable and interesting information, for it deals with the 

 final shaping of the American continent and the develop- 

 ment of its fauna ; but with this bare mention we must 

 be satisfied. 



Of the two volumes of Monographs, one (No. xvii.) 

 has a melancholy interest, for it is the last work of " the 

 Nestor of American palseobotanists," Leo Lesquereux, 

 left barely complete at his death. The memoir on the 

 " Flora of the Dakota Group " has been edited by Prof F. 

 H. Knowlton. The Dakota group appears to correspond 

 more closely with the Cenomanian of Europe ; thus its 

 plants have an exceptional interest, since they " pertain 

 to an epoch in which, by the appearance of the dicotyle- 

 dons, the character of the flora of the globe has been 

 modified as by a new creation. The cause or reason of 

 this marked change remains still unexplained." The 

 flora described by Prof Lesquereux consists of 460 

 species, of which 429 are dicotyledons Sixty-six plates 

 illustrate their remains, and the volume concludes with 

 an analysis of the results of the investigation, which is of 

 interest to more than pateobotanists. We must, how- 

 ever, restrict ourselves to stating Prof. Lesquereux's con- 

 clusion : that the flora of North America is not the result 

 of migration in past geological times, but an indigenous 

 one. All the plants of the American Cenomanian (ex- 

 cept those of Ficus and the Cycads) might still find a 

 congenial climate in the United States between latitudes 

 30° and 40"^ — that is to say, in localities at most a very 

 few degrees (perhaps five) further to the south. Since 

 the Cenomanian epoch the land surface between the 

 Rocky Mountains and the Alleghanies has suffered no 

 physical change of importance, for the general absence of 

 drift deposits from these vast plains indicates that they 

 were not greatly affected even by the glacial epoch. 

 " The result has been a prolonged uniformity of climate 

 and, of course, the preservation of the original types of the 

 flora, subjected to some modification of their original 



