a J 
: st 
Mineralogy and Geology. 401 
between the crystal and the source of light, when both bands appear. 
Hence it is clear that in the passage from the liquid to the solid state 
gives of an 
absorption or emission spectrum. The solutions are colorless and have 
acid the relative properties of the oxyds may be determined by the 
method of indirect analysis. In conclusion, an elaborate analysis of 
gadolinite is given leading very precisely to the formula 2Y,Si+BSi or 
more simply Sik, if glucina be considered a protoxyd.—Ann. der Chemie 
und Pharm., exxxvii, 1, Jan. 1866, W. G. 
II. MINERALOGY AND GEOLOGY. 
h may be of interest to the scientific public, an 
account of which, by request of Prof. James D. Dana, I herewith trans- 
mit for the Journal. 
I first emigrated to Colorado in the year 1858. In passing up the 
Arkansas river I found, upon many of the nearly barren ridges and hills, 
about three hundred miles west of the Missouri river, fragments of indu- 
rated chalk intimately mixed with silex and containing nodules of flint. 
At that time I was travelling through an unknown region, with but five 
companions, and had no opportunity to examine the white bluffs to be seen 
in the distance. On approaching the base of the mountains we turned 
northward from the Arkansas, and crossed over the dividing ridge which 
separates the waters of that river from those of the Platte. In doing so 
I found a large portion of the rocks to consist of a white or whitish con- 
Am. Jour. 8c1.—Seconp Series, Vou. XLI, No. 123.—May, 1866. 
51 
