Review of Recent Geological Literature. 57 
physical characters of rock-masses, while there is no essential chem- 
cal change either in the rock-mass or in its constituents. 3. Metataxis, 
or changes of order of the constituents of the rock-mass, of which the 
phenomenon of slaty cleavage may be taken as a typical instance." 
The author concludes that the Archaean rocks "represent upon the 
whole the primordial (first formed) earth's crust, from which the 
siliceous materials of the sedimentary rocks have been for the most 
part derived." But he does not consider these ancient crystalline 
rocks to be the first sediments and crystallized by hydro-thermal 
agencies. He believes there was a pre-oceanic stage during which a 
crust was formed which would theoretically consist of quartz and 
orthoclase as the Laurentian granites really do. This, he says, leads 
to the further conclusion that the process by which the Archaean 
gneisses and schists were formed (so far as their essential mineral 
characters are concerned) was essentially 'diagenetic' rather than 
'metamorphic' If this be admitted such phrases as 'the highly met- 
amorphosed Archaean gneisses and schists' must be relegated to an 
obsolete nomenclature of geologic science." 
The various phenomena of regional and contact-metamorphism are 
discussed and some of the causes assigned or suggested as possible 
explanations of them are interesting to say the least. An instance is 
in regard to foliation. He says, ''we may come ultimately to associate 
the feeble foliation of the fundamental gneiss where it has not been 
interfered with by mountain building processes with the earlier solar 
tidal waves and the more pronounced foliation of the Archaean schists 
with the subsequent Zunar tidal waves of the magma." 
Although we may not agree with Mr. Irving in his conclusions we 
can not fail to read with interest his reflections upon "metamorphism," 
which interest is heightened by the suggestiveness of many of his 
undeveloped ideas. 
Geology of Colorado ore deposits. By Pkof. A. Lakes. The scope 
and purpose of this little volume of about 150 pages can be best 
expressed in the language of the author, "This treatise contains the 
substance of a series of elementary lectures delivered by the author 
to the students of the Colorado State School of Mines. It is published 
with a view of meeting some of the needs of the general public, of the 
ordinary miner, and of the unscientific many, rather than with any 
idea of offering original matter for the discussion of the scientific few." 
In carrying out the purpose as above set forth, Prof. Lakes gives a 
succinct account of the successive geological formations, illustrating 
this part of the subject when practicable by references to outcrops 
and exposures of the successive strata within the limits of Colorado. 
The most valuable jiart of the work deals with tlie distribution and 
modes of occurrence of Colorado ores. The lithological characters and 
geological age of the rocks in which ores are found are very fully 
discussed. The intelligent miner will find much valuable in- 
formation respecting the characteristics and origin of placers, 
