THE OVERLAND ROUTE OGDEN TO SAN PRAXCISCO. 193 



earth, formerly called infusorial earth, is white and looks hke chalk 

 but differs from chalk in that it is composed of sdica instead of 

 hme carbonate. It has also been called tripolite, from Tripoli, 

 where a similar deposit is found. It is so Ught that it will almost 

 float on water. 



"Ir 



Near Lawton's hot sprmgs granite projects through the sediments, 

 and the fresh rock is exposed in cuts along the railroad. The outcrop 



is characteristic of rock of this type, consistmg of 

 Lawton. woatlier-rounded joint blocks that look like big 



Elevation 4,650 feet. bowMors but are reaUy a part of the sohd rock in 

 Omaha 1,545 miles. place. Beyoud the granite stream banks and rail- 

 road cuts reveal graTol, sand, and bowlder deposits, generally coarse 

 and ill assorted but with nearly horizontal bedding. These are old 

 river deposits, cut into by later deepening of the river channel. 



At the bridges near milepost 234, by which the wagon road and rail- 

 road cross the river, and particularly at the wagon bridge over the 

 railroad, is an interesting exposure of some of the tilted Tertiary strata. 

 Here the beds consist of shale and sandstone and justify their usual 

 designation as ''lake beds'' by their uniform thin bedding or lamina- 

 tion. They contain abundant and well-preserved impressions of 

 leaves and grasses. These beds arc believed to represent the Miocene 

 epoch of Tertiary time. Beyond the bridge these sediments are again 

 covered by terrace deposits. 



Verdi is a lumber town whose history dates back to the days of the 

 Comstock, before the coming of the raHroad, when many of the tim- 

 bers that went up to the mines were brought from this 

 Verdi, Nev. p^^^ ^f ^^ig mountains and hauled by way of Reno. 



Elevation 4,904 feet. Wcst of Vcrdi, strctchiug uorth and south as far as the 



Omaha 1,550 miles. eye cau SCO, is the steep front of the Sierra Nevada, 



this part of which is known as the Carson Range. 

 The front is determined primarily by faults. (See explanation of 

 formation of Wasatch Range, in footnote on p. 100.) The Truckee 

 emerges from the mountain front after travei-bing a naiTow canyon, 

 steeper and more rocky than hny part of its lower couree. Scattered 

 timber here clothes the mountain flanks, extending down even to the 

 raih*oad and river although, of course, all the older and larger trees 

 were long ago cut away. The green pines with their long needles and 

 the growth of underbrush afford a welcome change from the monoto- 

 nous barrenness of the ranges and plains of the Great Basin. There 

 is some cultivation in a small way along the narrow strip of river 



bottom lands. 



On leaving Yerdi the railroad turns southward up into the Truckee 



becomes so narrow that there is not room 



and 



^ 



the range 10 miles or more fai 



92213°"Bull. 612—15- — ^13 



oms 



