124 Expedition to the 



Soon after we had mounted our horses in the afternoon, a 

 violent thunder storm came on from the northwest. Hail fell 

 in such abundance as to cover the surface of the ground, and 

 some of the hailstones, which we examined, were near an 

 inch in diameter. Falling with a strong wind, these heavy 

 masses struck upon our bodies with considerable violence. 

 Our horses, as they had done on a similar occasion be- 

 fore, refused to move, except before the wind. Some of the 

 mules turned off from our course, and had run more than 

 half a mile before they could be overtaken. For ourselves, 

 we found some protection, by wrapping our blankets as loose- 

 ly as possible around our bodies, and waited for the cessa- 

 tion of the storm, not without calling to mind some instances 

 on record, of hailstones, which have destroyed the lives of 

 men and animals. It is not improbable, that the climate of a 

 portion of country, within the range of the immediate influ- 

 ence of the Rocky Mountains, may be morestibject to hail- 

 storms in summer, than other parts of the continent, lying in 

 the same latitude. The radiation of heat from so extensive a 

 surface of naked sand, lying along the base of this vast range 

 of snowy mountains, must produce great local inequalities of 

 temperature: the diminished pressure of the atmosphere, and 

 the consequent rapidity of evaporation, may in these elevated 

 regions also be supposed to have an important influence on 

 the weather. We have not spent sufficient time in the coun- 

 try near the eastern border of the Rocky Mountains, to enable 

 us to speak with confidence of the character of its climate. 

 It is, however, sufficiently manifest that in summer it must 

 be extremely variable, as we have found it; the thermometer 

 often indicating an increase of near fifty degrees of tempera- 

 ture, between sunrise and the middle of the day. These ra- 

 pid alternations of heat and cold must be supposed to mark 

 a climate little favourble to health, though we may safely as- 

 sert that this portion of the country is exempt from the ope- 

 ration of those causes, which produce so deleterious an at- 



