CAMPBELL'S SOIL CULTURE MANUAL 133 



April, if they immediately cultivate their surface soil and 

 get it completely dried out, they thereby conserve the 

 moisture, because any subsequent loss through evapo- 

 ration will have to come from evaporation within the soil, 

 and that is very slow, although slow evaporation does take 

 place within a soil. If you fill a tumbler with moist soil 

 and put it in the window in the sunshine, you will find 

 that the heat of the window sill frill make the temperature 

 of the bottom of the soil higher than the temperatiure of 

 the surface; you will then get evaporation from the bottom, 

 and the bottom soil will dry out quicker than the top." 



He did not explain, however, the direction which the 

 vapor takes which he says is in the soil. Evaporation 

 takes place only when there is some open avenue of escape 

 for the water in the form of vapor. There is no evapo- 

 ration from a hermetically sealed box. 



It was no doubt a matter of great surprise to Prof. 

 Whitney, as it has been to many others, to find crops 

 grown in the semi-arid country without any rainfall during 

 the growing season. They had a right to feel surprised 

 when they scraped off the surface with their hands and 

 found moist soil just beneath, and this where there had 

 not been rainfall for months. And investigation would 

 have shown exactly why the store house for water still 

 had a supply on hand for the use of the growing plants. 

 We have gone to many of our fields in Nebraska, Kansas 

 and Colorado during similar periods, with doubting Thom- 

 ases, who were equally as surprised as was Prof. Whitney, 

 especially in 1894-5, and also 1901-2. 



DRAWBACKS TO THE HUMID REGION. 



The story of the California tobacco crop was told to a 

 company of Maryland farmers, and continuing in response 

 to questions, Prof. Whitney further explained: 



" Conditions here are rather unfavorable for the con- 



