266 The American Geologist. October, looi. 
and that instead of increasing in value with depth all veins, 
in primal conditions, show diminishing values at great depths, 
until they are finally abandoned. 
Prof. T. C. Chamberlain gave a memorable discussion of 
the nebular hypothesis of La Place, summing up some of the 
results of his investigations continued through several years. 
From dififerent points of view he finds that the nebular hy- 
pothesis is untenable when subjected tO' the test of modern 
means and methods of science. He showed that the spiral 
nebula is a nonnal condition of primordial matter, much more 
common in the heavens than has been supposed. The abandon- 
ment of the nebular theory would require the reconstruction 
of much astronomical as well as geological theory as to the 
origin of the earth. 
The geologists present are very much indebted to the local 
geologists of Colorado for the success of the meetings. Of 
these should be mentioned Profs. Geo. L. Cannon, H. B. Pat- 
ton, F. W. Cragin, Arthur Lakes, George H. Stone. 
GEOGOLICAL EXCURSION IN COLORADO. 
Preceding the Denver meeting of the American Associa- 
tion for the Advancement of Science, a ten days' excursion 
was taken through Colorado. The excursion was under the 
auspices of Section E. of the A. A. A. S., and with the co- 
operation of the Geological Society of America. Leaving 
Denver on the morning of August i6th and returning to that 
point on the morning of August 26th, the party visited a 
number of localities important as centers of geological and 
mining interests. Mr. C. R. Van Hise was the leader of the 
excursion, and he was ably assisted by Mr. S. F. Emmons on 
ore deposits and general geology, and by Mr. T. C. Chamber- 
lin on glacial and physiographic geology. 
The first stop was at Canvon Citv where a visit was made, 
under the guidance of Mr. J. P. Hatcher, to the famous di- 
nosaur quarries. The Lower Silurian beds, in which the 
earliest known vertebrate remains have been found, were ex- 
amined, and some of the typical "hogbacks" were studied. 
From Canyon City the party walked through the Royal gorge 
of the Arkansas which is cut in a complex of Pre-Cambrian 
gneisses and granites. 
At Aspen visits were made to some of the prominent 
mines and the main features of the district — one which has 
been much faulted — were noted. 
The latter part of the trip was spent in the San Tuan dis- 
trict, stops being made at Ouray, Telluride and Silverton. 
This is a very mountainous district, where erosion has cut 
deeplv into the sedimentary rocks, which vary in age from 
Pre-Cambrian to Tertiary and which are capped by great 
