518 



GEOLOGICAL SUEVEY OF THE TEREITOKIES. 



EESULTS COMPILED FROM THE FOEEGOING TABLES. 



TilkPERATURE. — Temperature has beeu regarded in tlie work of ob- 

 servation, and a daily record kept. The greatest heat indicated was 

 97° Eah., August 17, 3.15 p. m., at Boteler's Eanch, Yellowstone Valley. 

 The greatest cold, 14P Eah., August 10, sunrise, at Yellowstone Lake. 



Moisture in the Atmosphere. — The record of the wet and dry 

 feulb thermometers furnishes many examples of large differences, indi- 

 cating an extreme dryness of the air. The greatest difference was 

 37^o, (dry-bulb 97°, wet-bulb 59Jo,) August 17, 3.15 p. m., at Boteler's 

 Eanch, Yellowstone Valley; elevation, 4,925 feet. 



Eain. — The number of days during which rain fell was 30 : in June, 

 7 ; in July, 11 ; in August, 9 ; in September, 2. Observations commen- 

 cing June 10. 



In the foregoing aggregate are included the thunder-storms accompa- 

 nied by rain. The amount of rain which fell was slight in nearly every 

 case. At Evanston we experienced a severe storm of wind and rain, 

 which was attended by a curious rising of the barometer. In fact, so 

 much was it affected as to be totally unreliable in its readings for eleva- 

 tion ; consequently, it was set aside entirely, and the elevation deter- 

 mined by the Union Pacific Eailroad Survey was adopted. 



Thunder-storms. — Five thunder-storms were experienced as fol- 

 lows : three in June ; two in July. We recorded distant thunder, indi- 

 cating a storm, upon seven other days ; in June, 6 ; in August, 1. 



Snow. — Snow fell in small amount at Yellowstone Lake, August 12. 



Hail. — Hail was noted at Boteler's Eanch, August 6. 



Frost. — A very heavy frost at Yellowstone Lake, August 13, was 

 recorded. 



Aurora Borealis.— Only one display of aurora borealis was noted, 

 June 17 and 18, and this was not remarkable in its character. 



Direction of ivind for tlie month of June. 



