32 Revietos — Dr. Hal/den's Oeological Reports. 



the Geological Society of London, by Mr. T. Gr. B. Lloyd.^ In this 

 paper Mr. Lloyd described the gravels of the Avon Valley between 

 Tewkesbury and Eugby, and of the Severn Valley above and below 

 the town of Worcester. 



The absence of horizontal sections, to illustrate Mr. Lucy's paper, 

 is to be regretted, for although he explains that, owing to the small- 

 ness of the scale, it would be difficult to show the different kinds of 

 gravel in a satisfactory manner, yet we cannot see why, with the 

 vertical scale magnified, they could not have been rendered as clear 

 as those which so admirably illustrate Mr. Codrington's paper in 

 the November number of the Quarterly Journal of the Geological 

 Society. 



II. — American Geology. 



(1.) Geological Eepokt on the Yellowstone and Missouri 

 EivEKS. By Dr. F. V. Hatden. Washington, 1869. 



(2.) United States Geological Survey Eeport on Colorado 

 AND New Mexico. By P. V. Hayden. Washington, 1869. 



TAKEN together, these two reports present us with a more or less 

 detailed description of the geology of a broad strip of country, 

 extending from New Mexico on the South, to the British possessions 

 on the North, and bounded on the West by the Eocky Mountains, 

 and on the East by the Lower Missouri. The Northern half of this 

 large area has been considerably more elaborated than the rest, and 

 Dr. Hayden speaks of his report respecting it as being the final one. 

 That on Colorado is merely a preliminary report; and, in the absence 

 of figures or maps, is not always by any means as clear as might be 

 desired, especially as many of the localities mentioned are not to be 

 found in ordinary maps. Added to this, the narrative form given to 

 both reports (the various sections, etc., observed being noted imder 

 successive dates) renders their perusal somewhat laborious, and 

 detracts not a little from their unquestionable value. These draw- 

 backs apart, however, the two thin volumes will be welcomed by 

 every geologist as the first really scientific description of a large and 

 important tract, which, until quite recently, was a perfect terra 

 incognita, so far as science was concerned. The mere amount of 

 hard work which they represent is enormous ; and the chief points 

 elicited by it are not only of local, but, in many cases, of general 

 interest also. 



Quite remarkable aj)pears to be the simplicity of the stratigraphical 

 arrangement of the sedimentary rocks in the Northern district, which 

 affords a key to their distribution in the somewhat more intricate 

 area of New Mexico and Colorado. The backbones of the main 

 ridges, and the cores of the isolated hills belonging to the Eocky 

 Mountain system, are universally composed of granitoid rocks, and 

 on their flanks all the stratified deposits seem to be uniformly ex- 



1 " On the Superficial Deposits of Portions of the Avon and Severn Valleys and 

 adjoining Districts." Quart. Journ. Geol. Soc, May, 1870. 



"We should also recall attention to Mr. Lucy's paper " On the Post- Pliocene Drift 

 of Charnwood Forest," published in the Geol. Mag. for November, 1870, p. 497. 



