58 
485 Le Conte (Joseph). A century of geology. 
Smith Inst., Ann. Kept, for 1900, pp. 265-287, 1901. 
480 Ledoux (A. R.). Notes on the Oregon nickel prospects. 
Can. Mg. Rev., vol. 20, pp. 84-85, 1901. 
Can. Mg. Inst., Jour., vol. 4, pp. 184-189, 1901. 
Describes the geological relations of the ore bodies and gives a chem- 
ical analysis of the ore. 
487 Lee (Willis T.). The Morrison formation of southwestern Colo- 
rado. 
Jour. Geol., vol. 9, pp. 343-352, figs. 1-4, 1901. 
Describes the character and occurrence of the Jurassic and Cretaceous 
strata of the region, and discusses the stratigraphic and paleontologic 
evidences of the age of the Morrison formation. 
488 L'Hame (Wm. E.). Thunder Mountain, Idaho. 
Mines and Minerals, vol. 21, p. 558, 1901. 
Describes briefly occurrence of gold in the region. 
489 Leith (C. K.). Summaries of current North American pre- 
Cambrian literature. 
Jour. Geol., vol. 9, pp. 79-87, and 441-458, 1901. 
490 - - Van Hise (C. R.) and. The Mesabi district. 
See VanHise (C. R.), 759. 
491 Leonard (Arthur Gray). The basic rocks of northwestern Mary- 
land and their relation to the granite. 
Am. Geol., vol. 28, pp. 135-176, pis. 15-19, 1901. 
Describes the geologic occurrence and relations and discusses the 
origin of the various facies. 
492 LeRoy (Osmond Edgar). Geology of Rigaud Mountain, Canada. 
Geol. Soc. Am., Bull., vol. 12, pp. 377-394, pis. 33-34, 1901. 
Abstract: Science, new ser., vol. 13, pp. 136-137, 1901. 
Describes the topographic and general geologic features of the region 
and the microscopic characters of the igneous rocks. 
493 Letson (Elizabeth J.). Post-Pliocene fossils of the Niagara River 
gravels. 
Buffalo Soc. Nat. Sci., Bull., vol. 7, pp. 238-252, figs. 161-190, 1901. 
494 Leverett (Frank). Old channels of the Mississippi in southeast- 
ern Iowa. 
Annals of Iowa, April, 1901. (Not seen.) 
495 Lindgren (Waldemar). Metasomatic processes in fissure veins. 
Am. Inst. Mg. Engrs., Trans., vol. 30, pp. 578-692, fig. 1-30, 1901. 
Abstract: Am. Jour. Sci., 3d ser., vol. 11, pp. 243-244 (£ p.), 1901. 
Discusses the general features of the changes in rocks contiguous to 
ore-bearing fissures, and the minerals developed by metasomatic proc- 
esses in fissure veins. Gives an account of fissure veins in various 
mining regions classified according to metasomatic processes. 
