GEOLOGICAL SUEVEY OF THE TEEEITOEIES. 



tlie miners found in the bed rock numerous " pot holes," with large 

 rounded masses, six to twelve inches in diameter, in the cavities. Some 

 of these spherical masses were basalt and others composed of a sort of 

 basaltic sandstone. 



Eemains of a species of elephant, probably UlepJias primigenius, 

 were found in the auriferous gravel, twenty-five feet below the sur- 

 face. A large tusk, with a number of teeth, ribs, and fragments 

 of bones, was found. I am indebted to Judge Lovell for the gift of a 

 fine collection of these remains, which are now safely secured in the 

 museum of the Smithsonian Institution. The tusk is especially remark- 

 able, and was preserved with great difficulty. These fossils have been 

 found in other portions of Montana, in the gravel, especially in the Last 

 Chance Gulch, near Helena, where a large quantity of these valuable 

 fossils were discovered. 



One tooth is said to have had a portion of the jaw-bone attached, and 

 to have weighed twelve pounds. The bones, as well as the teeth, seem 

 to have been partially worn as if they had been drifted about by the 

 waters to some extent, and I think they were washed from the latest 

 of the modern Pliocene deposits, which are abundant all over Montana. 



From Virginia City we traveled up a deep ravine to the divide that 

 overlooks Madison Yalley. The highest point over which the road 

 passes was found to be 6,857 feet. None of the mountains on this divide 

 were more than 800 to 1,200 feet above this altitude. On the east side 

 of Madison Yalley, there is a fine lofty range of mountains, the summits 

 composed of limestones, inclining west, while at the base, and extending 

 high up the sides, are grassy slopes, which give to the valley an 

 attractive appearance to the eye. Along the Madison Eiver, in this 

 X)ortion, are the first series of terraces yet observed. On the west 

 side are three of these terraces or steps ; four, if the broad bottom is 

 counted. The first terrace is 25 feet above the river, with an average 

 width of half a mile ; second terrace, average width one mile, 100 feet 

 above the first; third terrace 50 feet above the second ; and the fourth 

 200 feet above the bed of the river. These terraces are much more like 

 table-lands on the east side than on the west. On the west side of the 

 Madison, on the divide, the limestones extend over from the head of 

 Alder Gulch across the Madison to the eastward. The mountains 

 between the Stinking Water and the Madison Valley are not high, but 

 extend about northward to the Jeiferson in the form of a ridge, com- 

 posed almost entirely of granitoid rocks, with outbursts of basalt, and 

 here and there patches of 

 Pliocene deposits. The 

 dividing ridge between the 

 Jefferson and the Madison 

 Elvers varies from twenty 

 to thirty miles in width. 

 Outcroppings of massive 

 gneiss project up here and 

 there over the entire ex- 

 tent, giving to the surface 

 a rugged but picturesque 

 appearance, (Fig. 8.) The 

 limestones and quartzites 

 are nearly or quite all strip- 



peu on, anu tne more yield.- gneissic strata weathered out between madison river 

 ing portions of the granite ^^^ gallatin, on elk creek. 



rocks have worn down, and the surface smoothed and grassed over, so 



