January 1, 1897.] 



SCIENCE. 



15 



terrupted by the war, in. whicli he served 

 as surgeon in the army, and his report was 

 submitted in 1867, but not printed until 

 1869. With this was a geological coloring 

 of Eaynold's topographical map, which 

 gives in a very generalized form the current 

 ideas with regard to the geology of the 

 country east of the mountains. It shows 

 the anticlinal structure observed in the 

 Black Hills extended to all the ranges 

 facing the plains. In the interior, granites, 

 igneous and metamorphic rocks are all 

 grouped under one color, and no formation 

 between Carboniferous and Potsdam is 

 recognized. The age of the coal-bearing 

 beds is given as Tertiary. 



1867. I will mention here the contri- 

 butions of John LeConte in 1867, though 

 not strictly in chronological order, nor 

 under government auspices, yet they were 

 part of the general scheme of exploration 

 of the country for the projected Pacific 

 railroad. He was attached to the party of 

 Gen. W. W. Wright, of the eastern division 

 of the Union Pacific Railroad, which was 

 exploring various routes from Fort Lyon, 

 Kansas, to Fort Craig, New Mexico. He 

 made a more careful study of the coal- 

 bearing rocks than had yet been made, 

 and maintained his belief in spite of the 

 evidence of fossil plants as interpreted 

 by Lesquereux, that they were Cretaceous 

 rather than Tertiary, a belief founded 

 mainly on Molluscan fossils of Cretaceous 

 age found by him in association with the 

 coal beds, but in part also on a reason- 

 ing that the development of plant life in 

 this country had not been strictly contem- 

 poraneous with that of Europe. On this 

 point he says: " The difference between the 

 plants of our early Cretaceous and those of 

 the Middle Tertiary could be ascertained 

 only by the aid of the stratigraphy of the 

 region, and we have no right from a few 

 resemblances in vegetables to infer the 

 synchronism either of the Western lignite 



beds with each other, or any of them with 

 the European Eocene and Miocene, except 

 when supported by lithological evidence 

 from animal remains. 



" It would therefore appear plausible, in 

 the absence of more direct evidence, to be- 

 lieve that since the introduction of dicoty- 

 ledons in large numbers in our early Creta- 

 ceous there has not been any great change 

 in the types of structure ; and that such 

 changes, while following in general plan 

 those introduced on the eastern continent 

 during this period, have not been synchron- 

 ous with them." 



He noted several unconformities in the 

 beds, and presented a history of the oro- 

 graphic growth of the Great Plains in 

 Mesozoic time, which shows a remarkably 

 philosophical interpretation of the facts then 

 known. His idea was that the region grew, 

 by a series of gradual elevations connecting 

 Paleozoic islands, into one landmass; that 

 a great peninsula was developed running 

 eastward from the Rocky Mountains and 

 contracting the intercontinental Cretaceous 

 ocean. Thus by the end of the Middle 

 Cretaceous this ocean was divided into two 

 gulfs, a northern and a southern, in which 

 toward the end of that period the faunas 

 became quite different. Finally, independ- 

 ent shallow basins were formed in which 

 conditions for coal accumulation prevailed. 

 S. F. Emmons. 



U. S. GrEOLOGtICAL SUEVEY. 



( To he concluded. ) 



PHASES IN JA3IAICAN NATURAL HISTORY. 

 Prof. J. E. Duerden,* Curator of the 

 Museum of the Institute of Jamaica, has re- 

 cently published an article which gives new 

 and interesting data concerning the results 

 of the introduction of the Mongoose to the 

 Island. 



* Contributions to the Natural History of Jamaica. 

 By J. E. Duerden, Curator of the Museum of the In- 

 stitute of Jamaica. Kingston, November, 1896. 



