38 



appear along the low foot-hills. The dividing line should be taken on a parallel with the head of 

 Pahranagat Valley, although now and then a thin coating of snow has been known around Hyko. 



The northern section shows more variation of temperature; the division into the wet and dry 

 seasons is not so marked, and the intense cold noticed at high altitudes is in great contrast to the 

 heat of the summer's day in the valleys. The biennial rains occur, however, and snow frequently 

 appears instead of rain in the winter season. 



At altitudes not exceeding 7,000 feet, and there are but few points liable to be inhabited at a 

 much greater elevation, the maximum of temperature in summer will not exceed 100° Fahrenheit, 

 while in winter the mercury rarely falls more than 15° below the zero-point. 



Below the line of demarkation mentioned the biennial rains are strongly marked, occurring 

 principally in the months of July and January. After leaving our camp in Cave Valley, Septem- 

 ber 1, until reaching Indian Spring, October 25, there was not a single day of rain; at this point 

 there were a few showers, followed by clear sky, until White Pine was again reached. 



The thermometer in the heat of summer often reaches from 118° to 120° in the shade at mid- 

 day upon the Colorado. The clear, pure atmosphere, so extremely dry, renders this excess of tem- 

 perature more endurable than an atmosphere in the Eastern States not exceeding 95° Fahrenheit. 

 The glare of the sun, however, as reflected from the sandy washes and bare rocks, is very trying 

 to the eyesight. Ice at times formed at points as far south as Las Vegas Springs, but only in thin 

 films. It seems unfortunate that up to this time there should have been so few facilities for study- 

 ing the climatology of the great interior basins of the American Continent, which, of course, can 

 only be done after extensive series of atmospheric observations have been taken over long intervals. 

 It would seem not ill-advised that a system should be adopted by the Government in selecting 

 marked stations at which to commence and contiuue these series, though it be at considerable cost. 



The following-named mining-districts in Nevada were visited. The results of the examina- 

 tions will be published in Volume I, of the series of Reports, which volume will also contain all the 

 mining information gathered up to the close of the field-season of 1873. 



HEIGHT OF MOUNTAIX-EANGES. 



•This description must be limited to the most prominent of the ranges which have been 

 examined. 



HUMBOLDT RANGE. 



Beginning on the north, we find it to be the most remarkable and well-defined range that 

 belongs to this latitude, between the Sierras and the Wahsatch range. It has its northern limit at 

 the Central Pacific Railroad, near Humboldt Wells, and passing nearly due south, breaks away a 

 little below Hastings Pass, where it is traversed by the old overland road, into a succession of low, 

 broken hills and ridges, pretty well covered with cedar and nut-pine, fit for fuel. The highest peaks 



