440 KEMP AND BILLINGSLEY SWEET GRASS HILLS, MONTANA 



Lindgren,^ J. E. Wolff/ W. H. Weed, and L. V. Pirsson^ have furnished 

 descriptions. The numerous contributions of Weed and Pirsson to our 

 knowledge of these eruptive centers in the great plains constitute one of 

 the most striking series of investigations in both structural geology and 

 petrology which have appeared in recent years. The Sweet Grass Hills 

 were not described by them, although a short contribution was made 

 based on the early notes of Dr. George M. Dawson and on two specimens 

 of rocks from East Butte, two from West Butte, and one from an outly- 

 ing dike, all loaned by Dr. Dawson. The geographical relations of all the 

 eruptive centers mentioned above are shown on figure 7, pages 464, 465. 



Review of eaelier Work 



investigations of george m. dawson 



We owe to Dr. George M. Dawson the principal records hitherto made 

 on the geology of the Sweet Grass Hills. In connection with the Inter- 

 national Boundary Survey, carried on in 1873 and 1874, he visited the 



2 Waldemar Lindgren : On some eruptive rocks collected by the Northern Transconti- 

 nental Survey. Tenth Census Repts., vol. 15, 1886, pp. 719-737. Proc. California Acad. 

 Sci., Ser. II, vol. 3, pp. 39-57. 



— : A sodalite-syenite and other rocks from Montana, with analyses by W. H. 



Melville. Am. Jour. Sci., April, 1893, pp. 286-297. 



^ J. E. Wolff : Geology of the Crazy Mountains, Montana. Bull. Geol. Soc. Am., vol. 

 3, 1892, pp. 445-452. 



s W. H. Weed and L. V. Pirsson : Highwood Mountains of Montana. Bull. Geol. Soc. 

 Am., vol. 6, 1895, pp. 389-422. 



: On the igneous rocks of the Sweet Grass Hills, Montana. Am. .lour. Sci., 



October, 1895, pp. 309-313. 



: Igneous rocks of Yogo Peak, Montana. Am. .Tour. Sci., December, 1895,. pp. 



467-479. 



: Geology of the Ca.stle Mountain mining district, Montana. Bull. U. S. Geol. 



Survey, 1896, p. 139. 



: The Bearpaw Mountains, Montana. Am. Jour. Sci., April. 1896, pp. 283-301 ; 



May, 1896, pp. 351-362 ; August, 1896, pp. 136-148 ; September, 1896, pp. 188-199. 



: Geology of the Little Rocky Mountains, Montana. Jour. Geol., vol. 4, 1896, 



pp. 399-428. 



: Missourite, a new leucite rock from the Highwood Mountains. Am. Jour. 



Sci., November, 1896, pp. 315-323. 



: Geology and mineral resources of the Judith Mountains of Montana. I'. S. 



<;eol. Survey, 18th Ann. Rept., pt. iii, 1898, pp. 446-616. 



: Geology of the Little Belt Mountains, Montana. U. S. Geol. Survey, 20th 



Ann. Rept., pt. iii, 1900, pp. 271-461. 



: Geology of the Shonkin Sag and Palisade Butte laccoliths, iu the Ilighwoud 



:Mountains of Montana. Am. Jour. Sci., July, 1901, pp. 1-17. 



W. H. Weed : Fort Benton Folio, U. S. Geol. Survey, no. 55, 1899. 



: Little Belt Folio, idem, no. 56, 1899. 



L. V. Pirsson : Complementary rocks and radial dikes. Am. Jour. Sci., August, 1895, 

 pp. 116-121. 



: On the monchiquites or analcite group of igneous rocks. Jour, of Geology, 



vol. 4, 1896, pp. 679-690. 



: On the corundum-bearing rocks from Yogo Gulch, Montana. Am. Jour. Sci., 



May, 1897, pp. 421-423. 



