RAINFALL IN NEBRASKA. 49 



mean temperature of 68° 4'. My own determinations for the tem- 

 perature of the water of the Missouri at the same point, being a 

 mean of many observations for this month, give 63 9', showing 

 that the temperature of the water is for this month 4 5' lower than 

 that of the atmosphere. The mean temperature for July, 1 S77, at 

 Omaha, as determined by the signal office was 76 . For this month 

 the signal office also report the mean temperature of the river 73^°. 

 The temperature of the water at the Platte at its mouth, approxi- 

 mates more closely to that of the atmosphere, it being for June, 

 1S78, 6S° and for June 1879, 6f 9'. At North Platte the tem- 

 perature of the waters of the Platte is much lower, it being for 

 June 65 and for July 68°. It should also be remembered that the 

 temperature of the water is much more uniform than that of the 

 atmosphere. Its daily oscillations are small. It is rarely during 

 twenty-four hours the same as that of the atmosphere. From all 

 these causes then the evaporation from the surface is very great and 

 the winds carry the moisture in various directions, until finally it is 

 again deposited as rain. 



Nebraska Affected by the Amount of Precipitation of 

 Moisture in the Mountains. 



As the seasons of greatest rainfall in Nebraska are the seasons 

 of greatest rise in the Missouri and the Platte, and as the magni- 

 tude of these rises is dependent on the amount of snowfall in the 

 mountains, the moisture of the plains is to this extent dependent on 

 the amount of precipitation there during the winter season. A 

 question, therefore, in which every one here is interested, is 

 whether the amount of moisture there is decreasing, is station- 

 ary, or is on the increase. Some scientific authorities have ex- 

 pressed the opinion that the whole Rocky Mountain region is in a 

 comparatively rapid process of drying- up, and that the amount of 

 rain and snowfall must be less each decade and century. One of 

 the theoretical arguments presentedin proof of this view is, that in 

 ages geologically recent, the Rocky Mountain area was a region 

 of great lakes, and that it then lay at a much lower level, but that 

 now the lakes have nearly all disappeared, and that it is still rising 

 at the rate of a few feet to the century, and that, therefore, in the 

 nature of things, the drying-up process muvst continue. The facts 

 relied on for this opinion, are mainly that wherever the mountain 

 sides are from any cause denuded of their timber, no young trees 



