266 The American Geologist October, \ms 
The American Institute ov Mining Engineers met in 
Denver on September 2ist for its seventy-tlrst meeting. A 
large number of papers were presented, the following of which 
were more especially devoted to geology: 
Gold iu granite and ijlutonic rocks, U'. P. Blake. 
Rapid section work iu horizontal rocks, M. R. CamjJbeU. 
Faulting and accompanying features observed in glacial gravel and 
sand in Southein Michigan. (,V/r/ Heuricli. 
Traces of organic i-emains from theHuronian (?) series at Iron Moun- 
tain, Mich., IT. 6'. Uresleij. 
Magnetic observation in geological mapping, H. L. Smytli. 
According to Mr. L. S. Griswold (Bos. Soc. Nat. Hist., 
May 14, 1895), the basin of the lower Mississippi did not exist 
until the close of Cretaceous time. The fold of the Appala- 
(ddan Mts. swung westward as a land- barrier until pene- 
phiined in Cretaceous time, and the waters of the upper Mis- 
sissippi valley were emptied into a Permian and Mesozoic sea 
which existed toward the west. The post-Cretaceous elevation 
of the continent witnessed the extension of the river course 
toward the south instead of toward the west. 
Mr. Lewis G. Westgate, in a report on the geology of the 
northern part of Jenny Jump mountain, in Warren county, 
N. J. (Report of the State Geologist for 1895), concludes that 
the white crystalline limestones of that county, and inferen- 
tially of Sussex county, are not of the same age ms the blue 
limestones, but are pre-Cambrian, for the following reasons: 
1. They ditfer lithologically from the blue limestone in 
being thoroughly crystalline and in containing large amounts 
of accessory metamorphic minerals. 
2. They are intimately associated with and apparently 
interbedded with the older gneisses, and gneisses occur also 
interbedded in the limestones. 
3. They show no intimate association in areal distribution 
with the blue limestone, nor any tendency to grade into it. 
4. The metamorphic changes to which the white lime- 
stones have been subjected are general in their nature, and 
not due to the action of the eruptives by which they are cut, 
so that no sutlicient agent is at hand to account for the sup- 
posed change from blue into white limestone. 
The only apparent defect in the reasoning of Mr. Westgate 
seems to be in the assumption that the gneisses associated 
closely with the white limestones are pre-Cambrian. Further 
northeast, along the Appalachian fold are similar gneisses 
interstratitied with a white limestone which is of Cambrian 
age (if not later) as proved by discovered fossils. W^e refer 
to the Stockbridge limestone and its extension southward to 
the New Jerse}' state line. There is no known reason for its 
termination at Sussex county, nor Warren county. 
