250 Geology and Botany of Northern Pacific Railroad. 



slates" do not underlie the Potsdam in the Adirondacks, viz., 

 because the Potsdam is a sheet of sea-beach, produced by a wide- 

 spread, almost continental, depression of the land, or general ele- 

 vation of the sea-level, which carried the shore-line inland beyond 

 the areas where the Cambrian rocks had accumulated. 



The valley of the Missouri about Gallatin, and for nearly 100 

 miles below, is very broad and fertile, and is generally occupied 

 by farmers or stock-raisers. Wheat, rye, and especially oats are 

 successfully cultivated, but mainly by irrigation. All the low- 

 lands and the foot-hills of the mountains are covered with a fine 

 growth of bunch -grass, blue-stem and grama, upon which cattle, 

 sheep and horses are well sustained throughout the year. The 

 winters are long and severe, but not more so than in Minnesota, 

 and the snow-fall is somewhat less. The stock is not generally 

 fed or housed, though it would be more merciful and probably 

 more economical to provide some shelter. 



The Rocky Mountains. 



Helena, the capital of Montana, is a well-built and wealthy 

 town of some 8,000 inhabitants, located in and about the mouth 

 of Last Chance Gulch, one of the famous gold-camps in the 

 time of placer mining. 



The foot-hills of the first range of the Rocky Mountains, here 

 and northward to the British line, are composed of the palaeo- 

 zoic rocks which surround the Belt Mountains. About Helena, 

 they are generally limestones, somewhat metamorphosed, but 

 not much broken up. The various ravines which lead to the 

 Missouri valley, head in the granite rocks of the core of the 

 range ; and near these, the palaeozoic series is very much dis- 

 turbed. The granites, as well as some of the sedimentary 

 rocks, are traversed by many mineral veins, some of which are 

 auriferous and have furnished the large amount of gold that has 

 been taken from the gulches. Most of the mineral veins are, 

 however, silver-bearing, and these form a number of groups 

 where there are, or will hereafter be, prosperous mining camps. 

 At Wickes, twenty miles south of Helena, are numerous mines 

 now success. ully worked, and a very extensive plant for the 

 concentration and treatment of the ores by smelting and leach- 



