Geology and Natural History. 59 
chlorite is regarded by the author as of secondary origin, and as 
“introduced by the agency of water, which has permeated the 
the thin coating of Old Red Sandstone beneath, would become 
thoroughly impregnated with carbonate of lime, which it would 
deposit amongst the fissures and cells of the older rocks beneath.” 
to the surface ;* that the same is true for other 
? 
minerals formed, the chlorite excepted. ese cavities have 
nea Sometimes received mineral material from infiltrations of 
ter date, but not so the body of the roe J. D. D 
Taterior makes the following Report to te age 
The first division of the survey under Mr. Hayden completed 
the unfinished work of the preceding season in the central portion 
i Colorado Territory, and extended its operations westward over 
Pe The Conclusion, as far as it regards the trap of the Connecticut Valley, is sus- 
here _ by the microscopic researches of Mr. E. 8. Dana, an abstract of whose 
T 18 given on page 390 of the last volume of this Journal. 
