198 Review of Rnrnt Geological Liierature. 
more or lesa altered phases of the origiual basic eruptive?. The origin«l 
rock series, as has been said, dijw to the north ; the dykes dip to the south, 
and the angle between the dj-kes and tJieorii^iual beds of stratification is 
snch that if the strat^'fied rocks were placed again in a hoiizontol position the 
dykes wovld be veUical. The ore bodies rest upon a foot-wall of tilted 
-quartzite and lie in the apices of the V-ahapf>d troughs formed by the 
quartzite and the intersecting dykes. The iron ore is a soft, red, often 
porous, somewhat hydrated hematite, more or less manganiferous. The 
position and shape cf the ore deposits preclude the possibility of original 
sedimentation in place, as well as the possibility of their having been de- 
rived by oxidation from iron carbonate in place. There is an abunbance 
of iron carbonate in the iron-bearing formation but it is for the most part a 
lean ore containinix a large amount of silica. Iron carbi>nate was doubtless 
the source from which the hematite was derived, and the author shows 
how concentration from the siliceous carbonate may have occurred. 
Indeed in some parts of the series the process of concentration may be 
observed in all its various phases and stages. Narrow seams and crevices 
in the cherty carbonate are often found filled with a rich hematite. 
"Along the seams waters bearing iron in solution have passed. These 
waters have particle by particle dissolved out the chert and replaced it 
with iron oxide, and where once was lean sideritic chert is rich ore. A 
part of the iron oxide is due to the oxidation in place of iron carbonate, 
but the larger part has come from a greater or less distance there to be de- 
posited. The seams of iron oxide at this point are but a few in thickness, 
but it is probable that the series of changes which have here taken place 
•on a small scale, will upon a larger scale explain the concentration of 
workable ore-deposits." 
The possible mode of concentration of hematite in the apices of. the 
troughs already referred to is given at some length, with a very full and 
clear statement of the physical and chemical processes involved. 
The Great Lake Basins of the St. Lawrence, pp. ?i7-287. By A. T. Drum 
mond. (From the "Canadian Record of Science," January, 1889.) With a 
sketch map of the lake region. This paper is a cureful examination of the 
hypsometric and geological features of the basins of the great lakes with 
u view to reaching inferences touching their origin, age and vicissitudes. 
The topography of the lake bottoms is studied from the maps of the United 
States and Canadian surveys and soundings; and this, joined to the exist- 
ing topography of the land and the geological structure, points out certain 
conclusions here set forth. The substance of these is as follows: Gla- 
ciers had little efiect in the creation of the lake-basinS or even in shaping 
their present general outlines. The superficial deposits as others have 
maintained are less ihe product of glacier erosion than of secular disinte- 
gration since Carboniferous times. Lake Superior dates from Cambrian, 
Kewenian and lluronian times and as w;is first shown by Dr. Houghton, is 
in part at least, a synclinal trough; though volcanic action has had much, 
to do with its origin and the shaping of its coasts. Its early outlet was 
through WUitetish Bay, as long ago indicated by A. Winchell. Lako.^ 
