114 The Amei'ican Geologist. August, isoi 
globe, " leaving us to suppose that the lower portions were cooled 
and congealed earlier, j'et the circulation of the crenitic water is 
instituted and maintained by the " cooling of the surface by radia- 
tion and the heating from Itelow. " 
The "greenstones" form the uppermost member of the pre- 
Taconic cr3'stalline rocks. The}' are characterized by their re- 
semblance to the supposed "residual stratum," i. e. , they contain 
in abundance the "insoluble oxide of iron and magnesia. " The 
author supposes, in partial accordance with the latest deductions, 
that these rocks are the result, first, of exoplutonic extravasation, 
and second, of the chemical deposition of magnesian silicates from 
solution derived from the action of waters on this extruded mate- 
rial. There is here apparent!}' another anomalous supposition in- 
troduced, in that the action of the surface waters on this basic 
matter removed the lime and magnesia which are said to pass in 
solution into the sea, leaving of course the siliceous elements 
undisturbed or at least not carrying them into the sea. Yet this 
basic matter is said to have been derived from the supposed "res- 
idual stratum " and must hence have been not very much unlike 
the basic primitive stratum on which the crenitic waters are sup- 
posed to have acted with a result almost the reverse. 
The author takes but little account of the grand physical struc- 
tures of the Arehean rocks, such as bedding, dip, compression, 
shearing, schistosity, and the various more minute features which 
are generally considered as indices of a long physical history and 
of the agency of mechanical forces in bringing these rocks into 
their present conditions. The idea of metamorphism from a 
stratified sedimentary origin is specially denied. The results of 
late microscopic research into the intimate structures are passed 
by in silence. 
These are some of the obvious difficulties which arise in the 
mind of the reader who attempts to digest the argument, and are 
not supposed to be insurmountable objections to the hypothesis — 
though sometimes hypotheses have been cast aside as worthless on 
no stronger evidence of inconsistency. 
EEYIEW OF RECEXT GEOLOGICAL 
LITERATURE. 
On the Nickel and Copper DeposlU of Sudbury, Ontario. I{y Alfred 
E. B.vRLOw, M. A. (of llie Geological Survey Dept.) This timely paper, 
which appears in the June number of the Ottawa Naturalist, deals in 
