EFFECTS OF HUMIDITY AND BAIN. 



53 



TABLE 1. Humidity of the air at four desert stations where dates are grown. 



1 Records of Dr. Amat for the years 1883, 1888, and 1889. 



2 Schirmer, Sahara, p. 64. 



3 Records of Weather Bureau Station, completed by A. J. McClatchie, Bui. 37, Ariz. Agr. Ex. Sta., 

 p. 209, average of five years' record. 



4 Boggs and Barnes,* Bui. 27, Ariz. Agr. Ex. Sta., p. 37, record for the years 1892-1894. The mean 

 for October is 36,3 per cent. 



The following averages show the amount of atmospheric humidit} 7 

 at Phoenix and Tucson, Ariz., for each month from the flowering to 

 the ripening of the fruit of the date palm, and a partial record from 

 GhardaTa, Algeria: 



TABLE 2. Mean relative humidity at desert stations during date season. 



The occurrence of a well-defined rainy season in July and August in 

 southern Arizona causes the humidity for those months to be much 

 higher than it is in the Sahara, where all three summer months are 

 very dry. 



The following table showing the average rainfall for each month at 

 Biskra and Ayata in the Sahara, at Phoenix and Yuma, Ariz., and at 

 Salton, in the Salton Basin, California, brings out this difference in 

 climate: 



TABLE 3. Mean monthly rainfall, in inches, at Biskra, Ayata, Phoenix, Ynma, and 



Salton. 



1 Records of M. Colombo, published by Marcassin in Annales de 1'Inst. Nat. Agronom., 1895, 10 years. 



-'Records of M. Cornu, read from charts exhibited at Paris Exposition. 1900. 4 years. 



^Records of the Weather Bureau, compiled by Thos. H. Means, Second Rep., Div. of Soils, U. 8. 

 Department of Agriculture, 1900, p. 292. 



* Records of the Weather Bureau, compiled by Prof. Alexander G. McAdie, California Climate and 

 Crop Service, April, 1901, 12 years. 



