CLIMATE. 261 



pieces of drift-coal scattered along the river's course and 

 the mountains on each side are full of minerals. 



One thing is lacking a reliable working population, 

 racially adapted to its climate. Not that it is unhealthy. 

 Contrary to what would naturally be expected, the bottoms 

 are unusually exempt from malarious fevers ; the sick-roll 

 of the garrisons at Fort Mojave, and other posts in them 

 averaging very light. Indeed, as a residence for sufferers 

 from pulmonary disease, the valley of the Colorado has 

 proved itself to be admirably adapted. To account for 

 such a general healthfulness in so hot and occasionally 

 humid a situation, several theories have been from time to 

 time propounded by medical officers stationed there; but 

 which, as a general thing, were more matters of conjecture 

 than capable of demonstration. The climatic obstacle to 

 white labour is the heat. I can, of my own knowledge, 

 give data by which the reader may judge of its intensity. 

 One night in August, when en route from Southern 

 California to Arizona, I found a Government survey party 

 encamped in the bottoms, and paid my respects to them. 

 It was not an unusually hot night for that locality. I had 

 spent many as hot, several much hotter there. It was 

 11 o'clock, and the thermometer at the camp was suspended 

 in the current of what little air was drawing down from 

 the mountains. When I looked at the instrument, the 

 column of mercury in that thermometer was up to 112 

 degrees of Fahrenheit ! In the daytime, when the sun's 

 rays pour down between the mountainous sides of the 

 valley, and the direct, reflected, and radiated heat accumu- 

 lates and concentrates, the temperature becomes scorching* 



