Geology and Mineralogy. 241 
ing geosynclinal trough, with such additions as may be assumed 
for loss by degradation, is sufficient. The accumulation began in 
the Cambrian, and ended, according to the present state of facts, 
with the Permian, taking for its completion all of Paleozoic time. 
Supposing the thickness of the deposits made to have been 50,000 
feet, and the time elapsed during the making 50,000,000 years, the 
mean rate of sinking was 1 foot in 1000 years. The isogeothermal 
plane consequently rose at the mean rate of 1 foot in 1000 years, 
and the expansion through the rise of temperature went forward 
correspondingly, so far as was possible. At this rate the heating 
and the expansion continued in progress during the 50,000,000 
years ; and still, through all that time, sinking continued as the 
mean result. Such a rate of rise in the isogeothermal plane is so 
extremely slow—a thousandth of a foot a year—that it is hardly 
probable that the expansion could have been resisted through the 
long era to appear catastrophically at the end of it; and unless so it 
would seem that something more tharfa rise in the isogeothermal 
plane was needed in order to make the deposits into 4 mountain 
range. 
The theory of mountain-making brought forward by Mr. Reade 
does not explain the inequilateral feature of most mountains. 
Like most others that have been presented, it takes little note of 
the system of events in the progress of the globe and the system 
of structure in the results of that progress. American geologica 
study has made out plainly that there was first, in the continent, 
Archean ranges of elevations of one or more epochs; that on 
the eastern border there were three or four other periods in the 
course of geological time when other ranges of elevations were 
made, but all parallel in general and often in special trend, with 
the Archean, although stretching on fora thousand miles or more. 
The facts are similar, so far asis understood, in Western America. 
Here is system, working from a beginning, under some continued 
method of progress, ending in making a continent of systematic 
features. Mr. Reade says that ‘ Dana looks upon the development 
of continental land as analogous to animal growth.” Nothing 
could be farther from the truth ; for all that the comparison used 
by the writer meant was that there was systematic progress, in 
some way, as much soas in animal development. There is system 
also in the courses of the feature lines of the globe, which courses 
are as far removed as possible from meridional as required by 
some theories. The fact that the writer formerly made all. 
these results to depend on contraction from cooling and the nature 
of the earth’s crust, shows that the accordance with animal growth, 
was only accordance with the universal law of progress or de- 
velopment (Man. Geol., p. 830). What theory now to attribute 
the results to he does not know; but he believes that no theory of 
mountain-making will find general acceptance that does not take 
this system of progress, of structure, of topographical features 
into consideration. If the speculator thinks, like Mr. Reade, the 
linear arrangement of islands of little importance, let him consider, 
