284 Scientific Intelligence. 
plates are very transparent, the double refraction strong, the dispersion 
feeble with g>v, and orientation of the optical axes uncertain because of 
. 
the irregular contour of the lamin. I have found, at 20° C, 
ii 
7. Geological Observations in Colorado. (Colorado Transcript, July 
24, 1867.)—The late railroad surveys on Dry and Boulder creeks, St. 
Vrain, Big Thompson and Cache-a-la-Poudre rivers, and on the South 
Platte, under Capt. E. L. Berthoud, have shown that the Cretaceous 
strata on the east slope of the Rocky Mountains, extend eastward from 
_ upper beds, extending some seventy-five miles from the Rocky Mountains, 
coal of good quality can be found in large fields, which near the mountains 
in Jefferson county are covered on its west border by almost horizontal Ter- 
tiary — and through which extensive outcrops of Cretaceous coal occur. 
8. Geologi 
cal Survey of Ne —By appointment from t Gene- 
ral Government, the geological survey of Nebr: just been com 
direction rofessor F, V. Hayden. Dr. Ha. 
C. A. White, its able state geologist; and this again directly west of Ili 
nois, whose geological survey under Dr. Worthen has already made great 
. of 
04° 
‘of the continent on this side of the Rocky Mountains to } 
regre of 
tS Maat Gr the Biteny o : including | 
Tague y of the Northern United States, wer’ 
the district Hast of the Mississippi and North of North Carolina and 
Tennessee, arranged according system ; by Asa Gish 
_ Hisher Professor of Natural History in Harvard University. Fifth gi 
sses 
ykeman & Co. Chicago: S. C. Griggs auly 
former editions of this Manual have ae ‘and 
