1895.] . Petrography. 365 
produced by the solution of some crystals of calcite or dolomite that 
remained for a time in the midst of the replacing silica after all the 
rest of the carbonate had been removed. 
Pearce” gives a series of analyses to sustain his theory that the free 
gold of the Cripple Creek District, Colorado, has been mainly derived 
from the oxidation of tellurides. 
In a preliminary report on the Rainy Lake Gold Region in Minne- 
sota and Manitoba, H. V. Winchell and U. S. Grant" give some brief 
notes descriptive of the Laurentian, Coutchiching and Keewatin rocks 
of the district. 
1 Golo. Scient. Soc., April 5, 1894. 
u 23d Geol. & Nat. Hist. Sur. of Minn., p. 36. 
