176 Prof. Chapman on some Minerals 



tions, the force of attraction would not change till the water 

 from the melted ice had had time to flow away towards the open 

 sea in the equatorial latitudes ; for the water derived from the 

 ice, though fallen down a few hundred feet into the channels 

 and lakes below in the general mass, would attract very much as 

 the ice itself did. And as the gradient of 1000 feet in 60° of 

 latitude is very slight, the tendency of the water to flow out and 

 of the sea-level to sink as the ice was turned into water would 

 be feeble, and the outflow much obstructed by the windings of 

 the channels and the countercurrents produced by impact upon 

 the enormous ice-fields into which the ice-sheet would at first be 

 broken. 



It appears to me, then, extremely likely that the supply of 

 water in the northern latitudes from the melting of masses be- 

 tween 3000 and 7000 feet high would be far more rapid than 

 the outflow of water owing to the solid mass becoming less ; 

 and the consequence would be that during the Drift Period the 

 ocean in the northern latitudes would stand at a much higher 

 level, for a considerable time, than 650 and 1000 feet in lati- 

 tudes 45° and 60°; and vast icebergs with huge boulders fixed 

 in their lower parts might find ample depth of water to carry 

 them over all the places where the phenomena of abrasion and 

 drift-deposit have been found. j jj Pratt. 



XXV. On some Minerals from Lake Superior. By E. J. Chap- 

 man, Ph.D., Professor of Mineralogy and Geology in University 

 College, Toronto*. 



A RECENT visit to the north-west shore of Lake Superior 

 enabled me to obtain several minerals of much interest, 

 including two or three species previously unrecognized in 

 Canada. Brief descriptions of these latter, with a few observa- 

 tions on some of the other minerals which occur in this region, 

 are offered in the following notes : — 



1 . Native Lead. — As a natural product, lead is well known to 

 be of exceedingly rare occurrence in the simple or metallic state. 

 On this continent — apart from its occurrence in the meteoric 

 iron of Tarapaca in Chili — it has hitherto been noticed only at 

 one spot, namely in a galena vein, traversing limestone (of un- 

 stated geological age), near Zomelahuacan, in the province of 

 Vera Cruz, in Central Mexico. The specimen from the locality 

 now under consideration was obtained at a spot near the cele- 

 brated Dog Lake of the Kaministiquia. The lead occurs in this 

 specimen — the only one, I believe, discovered — in the form of a 

 small string in white semiopake quartz. The quartz, which 

 * Communicated bv the Author. 



