Personal and Scientific News. 
407 
outlined the views that had already been published regarding their 
stratigraphical relations, especially those of Clarence King and S. F. 
Emmons of the 40th Parallel Survey, who referred them to the Pliocene, 
and those of C. A. White of the United States Geological Survey, who 
referred them to the Eocene. Mr. Irving stated that careful search 
failed to reveal any fossils except a few fragments of bone, which were 
in such a state that Dr. Wortman considered them to be not earlier than 
the Pliocene. Mr. Irving then described the Lodore canon and ex¬ 
plained the formation of the lake in which the Brown’s Park beds were 
deposited as due to the Pliocene elevation of the Uinta sandstone that 
forms the wall of the Lodore canon. When this was cut down by the 
river the lake disappeared and depositions ceased. He, therefore, cor¬ 
roborated the original determinations of King and Emmons. The paper 
will appear in full in the Transactions. 
The second paper of the evening was by Prof. C. H. Smyth, Jr. on 
“ The Origin of the Talc Deposits near Gouverneur, N. Y. n Dr. Smyth 
first described the geological surroundings of the talc and showed that 
it occurs along a series of belts in limestone walls and that the previously 
published statement that it occurs in gneiss is incorrect. By means of 
microscopic sections he traced its development by the alteration of trem- 
olite in largest part and from enstatite to a less degree, the changes in 
both having been affected through the agency of water and carbonic 
acid. The talc occurs in two forms,—a scaly variety, or talc proper, 
and a fibrous variety, or agalite. He was unable to determine whether 
the original rock was a basic intrusive or a siliceous magnesian limestone. 
The full paper will appear in the School of Mines Quarterly for July, 
1896. 
The third paper of the evening was by Prof. H. P. Cushing and was 
entitled ^ Are there Pre-Cambrian and Post-Ordovician Trap Dykes in 
the Adirondaeks?” Field work in Clinton county, N. Y. had convinced 
the writer that there were two periods of dyke intrusion in the Adiron- 
dacks. The first yielded the porphyries or bostonites, the camptonites 
and non-feldsnathic dykes, which cut the Paleozoic strata up to and 
through the Utica slate. These dykes are chiefly limited to the shores 
of lake Champlain both in New York and in Vermont. They practically 
lack diabase. The second set are limited to Archean rocks, are much 
more numerous and are practically all diabase. One hundred and six¬ 
teen dykes in all are known in Clinton county; sixteen belong to the 
first series, while the remaining one hundred belong to the second. The 
latter have been found in the gneisses in many cases very near the con¬ 
tacts with the Potsdam sandstone, but in no case have they been found 
penetrating the sandstone. The same relations have been noted by 
Smyth at the Thousand islands. 
Prof. Cushing, therefore, urged that these dykes should be considered 
a separate series of rocks that had been formed subsequently to the 
metamorphism of the crystalline rocks and before the deposition of the 
Potsdam sandstone. The paper will appear in full in the Transactions. 
J. F. Kemp, Sec’y. 
Geological Society of Washington. 
At the 48d meeting, held in Washington. D. C., April 22, 
1896, communications were presented a# follows: “A new 
laccolite locality in Colorado and its rocks,” by Mr. G. K. 
Gilbert and Mr. Whitman Cross; “The origin of some moun¬ 
tain scarps,” by Mr. M. R. Campbell. 
Mr. Gilbert described a laccolitic locality discovered last summer 
in southern Colorado. Dakota and older rocks are bent into a dome 
with a hight of 1,033 feet and a width of 5 miles. Many dikes traverse 
