1884.] 219 [Crosby. 



Mr. S. H. Scudder showed the photograph of the oldest fossil 

 insect yet known, a scorpion discovered in Gotland during the past 

 summer, in Upper Silurian beds, by Dr. Lindstrom. The fossil 

 differs from modern scorpions in the short, stout, tapering legs, 

 terminated by a single claw. 



General Meeting, Jan. 17, 1885. 



Professor A. Hyatt in the chair. 

 The following paper was read : 



COLORS OF SOILS. 



BY W. O. CROSBY. 



The usual colors of soils and of superficial detritus generally, — 

 the various shades of black, gray, green, blue, brown, j^ellow and 

 red — are well understood, resulting chiefly from the admixture in 

 various proportions of vegetable mould and more coal-like forms 

 of carbon, and of iron in the forms of ferrous salts and the various 

 hydrous and anhydrous oxides. My present purpose, therefore, 

 is not to undertake a general discussion of the colors of soils, but 

 to suggest an explanation of the marked contrast in the colors due 

 to the ferric oxides presented by the soils of high and low lati- 

 tudes. This general difference in color between northern and 

 southern soils is an unquestionable fact, and must be familiar to 

 many travellers ; and yet but few geological writers have even 

 mentioned it, and, so far as I can learn, no explanation of it has 

 heretofore been proposed. 



In all latitudes, the most superficial detritus, the true agricul- 

 tural soil, is, in a large measure, distinctly carbonaceous, or the 

 organic matter has at least been sufficient to more or less com- 

 pletely discharge the brown, yellow and red colors due to the ferric 

 oxides. But in the surface soil to a considerable extent, and in 

 the subsoil generally, the ferric oxides are still the predominant 

 coloring agents. Now, throughout the northern states and Can- 

 ada the soils, where their colors can be ascribed to ferric oxide, 

 are generally, almost universally, brownish or yellowish, but not 



