TEMPERATURE. 23 



As is shown by the foregoing table, the normal yearly maxima are 

 highest in the Jerid oases (Tozer and Nefta) and are lowest at Gabes, 

 on the coast. In winter the maxima are higher at Nefta, but lower 

 at Tozer than at Gabes. At Tozer the minima are higher for nearly 

 every month than at any other locality in Tunis, while at Nefta 

 those for June, July, and August are higher than at any other 

 locality excepting Tozer. Comparing Gafsa, which has an elevation 

 above sea level of 1,000 feet, with Gabes, on the coast, we find the 

 maxima higher at the former point in all seasons except winter. 

 The minima are lower at Gafsa than at Gabes in every month of the 

 year. 



A climatic factor upon which the success of date culture largely 

 depends is the sum total of heat received during the ripening period, 

 which can be taken as comprising the six months from May 1 to 

 October 31. As it is still a question whether the sum total of the 

 daily means or those of the daily maxima give the best expression 

 of this factor, both sums have been computed for the Tunis locali- 

 ties, and are given in the following table. Following the sugges- 

 tion made by Mr. W. T. Swingle, 6 the sums of the daily means are 

 based upon the excess of the normal monthly means over 64.4 F., 

 while in computing the sums of the daily maxima above 64.4 deduc- 

 tion has been made for normal monthly minima that fall below that 

 temperature. 



a As pointed out on p. 21, however, the results for Nefta and for Kebili are 

 based upon too short periods of observations. 

 Bui. 53, Bureau of Plant Industry, pp. 65-68. 

 92. 



