THE SCIENTIST. 
visit to that region last summer, 1 
reached the conclusion that the immense 
deposits of breccia to be seen there are 
the accumulations around an extinct 
sea, i. e., the gravel that indicated the 
beach line around such a sea. This 
breccia is composed of beautiful water- 
worn gravel of almost every color and a 
paste or matrix of alkali or alkaline 
earths and sand. This alkaline matrix 
in some instances is volcanic lime, and^ 
in others it is potassium salts. NTear the 
old abandoned fort, McRea, there are 
thousands of acres of this formation that 
show croppings from twenty to one 
hundred feet in thickness. The pebbles 
and gravel in the formation are some, 
times common brown or yellow chert, 
at others, white or clouded quartz, topaz, 
agate, chalcedony and occasionally an 
obsidian. 
The extinct sea theory did not satisfy 
niy reason, but 1 mentally accepted it as 
the best explanation! could give to myself 
at that time. My last two visitsto Colo- 
rado haveulforded the means of reaching 
a very different conclusion. All the 
brecc-ia, gravel, pebbles or pronounced 
drift that are so abundant in the "parks'' 
or wide valleys, on the mesas, deserts 
and mountain sides in the EocKy moun- 
tain region are undoubtedly of glacial or 
post glacial origin. The lidge or divide 
mentioned above, the one in eastern 
Colorado, is composed largely of drift 
materials. Here it occasionally takes 
the form of a breccia, but more often it 
consists of deposits of sand and gravel 
thrown losely together. There are three 
ways in accounting for this ridge. 
1. It is a ridge whose bed-rock was 
too hard to yield to the erosive influences 
of the ante -glacial waters that poured 
down the eastern slope of the Eocky 
mountains and thus remained in the 
waters as a bar. 
2. It is a terminal morraine or a series 
of terminals. 
3. It is a lateral morraine. 
If the first proposition is correct, the 
drift was deposited over the hard rock 
bar which already marked an elevation 
on the topography of the plains. These 
deposits would then only exaggerate the 
elevation. But I have failed so far to 
discover any hard bed-rock. On the 9th 
instant, I noticed where a tributary i f 
the Republican river crosses this ridge 
that the drift material is exposed to the 
river's bed. I conclude, therefore, that 
the first proposition is untenable or from 
data so hastily gathered is not satis- 
factorily established. 
The second proposition, a series of 
terminal morraines, seems, likewise un- 
satisfactory. It is improbable that a 
number of gl:iciers would have de|»osited 
such masses of material on so nearl}^ the 
same line. This could not have hap- 
pened unless the first clause of the tir.-t 
proposition is correct,that an ante-glacial 
ridge existed at the time of deposition. 
The facts adduced in discussing the first 
proposition seem to indicate the con- 
trary. 
The third proposition seems tenable. 
This is strengthened by the government 
reports which set forth the fact that the 
glacial drift and the glaciers themselves 
moved through Colorado in a south- 
easterly direction along the eastern slopes 
of the mountains, it is several years 
since 1 read these reports, but this is my 
memory of them. I may be treating a 
subject that has been exhaustively dis- 
cussed in some of these same reports, but 
so long as 1 am not aware of anything of 
the kind, I will proceed, not without 
realizing however that the ignorant fre- 
quently venture where the wise would 
desist. It seems probable to my mind 
that a large glacier paralleled the eastern 
base of the mountains. Near Denver it 
was moving in a southerly direction. 
This ridge is composed of the materials 
deposited along its eastern slope. As 
this glacier moved south, it gradually 
melted and became reduced in size. 
