192 



GUIDEBOOK OF THE WESTERN TNITED 



Leaving Reno tlio railroad rims west along the north side of Tnickoo 

 River, here again confined in a canyon, which, however^ is not so 

 narrow or steep as the canyon in the Virginia Range. The river is 

 bordered on hoth sides by a succession of terraces, the uppermost of 

 which is several hundred feet above the river bottom. In the out- 

 skirts of Reno, on the north side of the track, there is a clay pit and 

 brick plant, and beyond them are large pits that have been excavated 

 in the river terraces for sand and gravel to be used in construction 

 work. The site of Reno and much of the valley to the west is over- 

 spread by deposits of bowlder and gravel left by the river during the 

 period of terrace building. The open lands at the foot of the high 

 mountains permitted the streams to spread out and deposit the load 

 of bowlders and finer sediments that they had washed through the 

 steeper and narrower parts of their channels above. 



Projecting in places from beneath the nearly horizontal terrace 

 deposits are reguhirl}^ bedded, tilted sedimentary rocks^ the only 

 unaltered sediments of the Reno region known to be older than Qua- 

 ternary. They belong to a series of fresh-water deposits called 

 the Truckeo formation, generally considered of Miocene age. Tliese 

 beds, which consist of clay, gravely sand, and a pecidiar white earth, 

 are finely exhibited in conspicuous white bluffs 2 to 4 miles west of 

 Reno, and are worthy of particidar notice^ for the chalk-white earth 

 of which they are so largely composed here occurs in unusual quan- 

 tity. This^ chalk-white material consists largely of microscopic 

 shells, or frustules, as they are caUed, of one-celled plants knoA\Ti as 

 diatoms,^ once included under the general name Infusoria. These 

 remains have collected here in numbers so immense as to form 

 deposits hundreds of feet thick and in places make up almost the entire 

 mass of the rock. This mass of fossil diatoms, or diatomaceous 



between mineral veins and eruptive 

 rocks. Thermal waters are believed to 

 be, in part at least, given oS by slowly 

 cooling and solidifj'ing masses of igneous 

 rock (magma) deep within the earth. 



^ Diatoms are of many different forms 

 and inhabit both fresh and salt water. 

 They consist of single isolated cells, or 



of stnngs of cells attached i 

 cession or in zigzag chains, 

 compose the beds west of 

 tirely of fresh-water origin. 



that 



parts,each shell consisting of two 



diatoms 



tr li\-ing 



and 



cover. Seen under the microscope they 



and 



of structure. The myriads of such shells 



that accumulate after the death of these 

 plants may form large deposits, although 

 the individual shells are so minute as to 

 be undiscemible by the unaided vision. 

 Diatomaceous earth Is used largely as a 

 scouring or polishing powder, to which it 

 is well adapted because of the hardness 

 and sharpness of the individual grains 

 and their uniform fineness. It also has 

 uses dependent on its absorptive proper- 

 ties and has been so used in the manufac- 

 ture of dynamite. As it is a poor con- 

 ductor of heat and very light it is valuable 

 as a packing for safes, steam pipes, and 

 boilers, and for the manufacture of fire- 

 proofing materials. No use seems to 

 have been yet made of the deposits near 

 j Reno, 



