368 The American Geologist. June, 1892 
rocks of the crust may undergo and have actually experienced, 
such profound changes in average chemical composition that their 
original minerals may be entirely lost. Sometimes there is hy- 
pothecated a ‘‘silicification,’’ and sometimes a desilication. The 
most basic rocks have been viewed, in some of these critical 
epochs of mythical metamorphism, as converted, by a substitu- 
tion of ‘‘secondary silica’ for the typical minerals of the supposed 
original basic eruptive rock, to a quartzyte, or toa quartz dioryte. 
Gabbros have been imagined converted to quartz syenites, and 
the details of the process of such transition have been ingeniously 
imagined and illustrated, Quartz, the most insoluble of the rock- 
making minerals, has been supposed to have been conveyed into the 
minutest interstices of these rocks to the depth of hundreds or 
thousands of feet, there taking the places of some of the origina] 
minerals which, by a reverse but no more mythical chemical 
transformation, were removed by the same waters, or at least by the 
same process. Again the geologist has not to resort to “dynamic 
metamorphism” by which to account for the shattered and partly 
disintegrated or degraded condition of the minerals of the green- 
stones. It is at best only a misuse of the term metamorphism to 
apply it to such a change, and it may be considered questionable 
whether the cause which dynamic metamorphism invokes would 
not produce a directly opposite effect. It is usually supposed that 
pressure and crushing and shearing develop heat, and thus tend 
toward the building up of the crystalline outlines and the 
strengthening of the chemical bonds, in the minerals affected. It 
appears to some geologists not only a misnomer, but a mistaken 
apprehension of the effect of dynamic forces to attribute such 
features to pressure and shearing and plication, and to call it 
‘metamorphism.’ Such outre hypotheses can be shaken off the 
mantle of the speculative physical geologist, if he allow the building 
up of these rocks, as above suggested, through the cooperating, 
simultaneous action of oceanic waters and volcanic eruption. 
A NEW SPECIES OF LARIX FROM THE INTER-= 
GLACIAL OF MANITOBA. 
By D. P. PENHALLOW, F. R. 8S. C., F. R. M. S., McGill University, Montreal. 
Two specimens of fossil wood were recently received from 
Manitoba, the one from Mr. G. Elliott, of Guelph, Ontario, the 
other from Mr. J. B. Tyrrell, of the Geological Survey. The first 
was admirably preserved, and upon boiling with carbonate of 
