246 A LORS a VAS, SAKA CAES, 
Crystalline Limestones and Associated Rocks of the Northwestern Adi- 
rondack Region. By C. H. SMyTH, JR. 
Extensive belts of highly crystalline limestone constitute an impor- 
tant feature of the region. These belts are separated by wide areas 
of rather massive gneisses, whose origin and relations to the limestone 
are obscure, and afford the chief problem for future investigation. 
They are probably largely igneous. 
Rocks whose igneous origin has been clearly ascertained are scat- 
tered over the whole area. They are chiefly granite, diorite, gabbro 
and diabase. ‘These are all younger than the limestone, cutting it with 
typical irruptive contacts, often affording a variety of contact minerals. 
The most extensive igneous rock passes into a gneiss which spreads 
over a wide area and is quite similar to many of the other gneisses. 
This gives a clue to the origin of the latter. Some of the granites 
- are suggestive in the same direction. 
Much crumpling and crushing in the limestone series is indicative 
of dynamic metamorphism, but should most of the gneisses prove to 
be intrusive it would strengthen the hypothesis of thermal metamor- 
phism on a large scale. 
U.S. Geologic Atlas, Folio 1, Livingston, Montana, 1894. 
This folio consists of three and one-fourth pages of text, a topo- 
graphic sheet (scale 1:250,000), a sheet of areal geology, one of 
economic geology, one of structure sections, and one giving a columnar 
section. The text is signed by Joseph P. Iddings and Walter H. Weed, 
geologists, and Arnold Hague, geologist in charge. 
The area of country covered by the folio lies between the parallels 
of latitude 45° and 46° and the meridians 110° and 111°, and 
embraces 3340 square miles. It is within the state of Montana, 
including portions of Gallatin and Park counties, and the town of Liv- 
ingston is within its limits. The region is elevated, the lowest point 
being over 4000 feet, the major portion over 6000 feet, and the high- 
est peaks over 11,000 feet, above sea level. 
The principal topographic features are the Snowy Mountains, Gal- 
latin Range, Bridger Range, Crazy Mountains, and Yellowstone 
Valley. The Yellowstone River is the main drainage channel for 
the area. It enters the district from the Yellowstone Park about the 
middle of the southern border, lows northwest and north through a 
closed valley thirty miles long and three miles wide, and at Livingston 
