Jourttal of Travel and Natural History 327 



^isccUaup. 



Geology of Central North Araerica.* — Last year the Union 

 Pacific Railway Company, Eastern Division, made an important survey for an 

 extension of their line from the Smoky River, Kansas, to the Rio Grande, and 

 with a liberal appreciation of the value of scientific discovery, they attached 

 one or two naturalists and geologists to the surveying party. The head of this 

 scientific department was the well-known naturalist of Philadelphia, Dr J. L. 

 Leconte, and he has just published a summary of the Geological Obsei^vations 

 made during the expedition, under the title given below. This is little more 

 than a business report for the use of the Company and practical men, Dr 

 Leconte considering that science will be better sei-ved by the more detailed 

 results being published in another form at a later time ; but, while his "Notes" 

 are chiefly of this nature, he gives at the conclusion a brief sketch of the general 

 inferences which may be drawn from the facts observed, from which the reader 

 may judge of the philosophic spirit in which the inquiry has been conducted, 

 and of the interest which will attach to a more deliberate and complete account 

 of his observations. Dr Leconte's summary of the Geologico-Historical con- 

 clusions is as follows : — " 1st, That the development of the present structure 

 and surface of the continent from the Rio Grande, eastward to Kansas, has 

 been by a series of gradual and extended elevations from the south to the north, 

 lifting large tracts of land above the surface of the ocean, and connecting the 

 islands of the Palaeozoic age into a mass of land gradually growing towards 

 the north and east. 2d, That the greater part of this elevation in the south 

 took place at the end of the lower Cretaceous period, and was accompanied with 

 upheavals of one or more mountain chains ; that similar phenomena occurred 

 further north, at the end of the Cretaceous or in the early tertiaiy. 3d, That after 

 the first and during the middle Cretaceous period, the continent was developed 

 further by the formation of a great peninsula, running eastward, contracting the 

 inter-continental Cretaceous ocean, and preparing it for the division into two gulfs, 

 which was finally accomplished at the end of the middle Cretaceous. 4th, As 

 a i-esult of this division of the inter-continental ocean, the fauna of the two 

 gulfs became quite different in the latter Cretaceous period ; so that but few of 

 the fossils of that time are common to the Missouri basin, and the regions south 

 of the Arkansas. 5th, During this gradual progress of the continent towards 

 the east and north, circumstances favourable to the accumulation of beds of 

 lignite occurred successively at different places, giving rise to independent 

 basins : those of the Rio Grande belonging to the lower Cretaceous, those of the 

 Raton (as shewn by the Inoceramus) to the middle Cretaceous, those of the 



* Notes on the Geology of the Survey for the Extension of the Union Pacific 

 Railway, Eastern Division, from the Smoky Hill, River Kansas, to the Rio 

 Grande. By John L. Leconte, M.D. Philadelphia, 1868. 



