232 DISCUSSION OF THE DESICCATION QUESTION. 



Palestine has changed within the past 3,000 years, as has been abundantly 

 proved in the preceding pages. The land once described as " flowing with 

 milk and honey" is now dry, and for the most part little better than a desert. 

 If the mean temperature has not changed, the supply of moisture has cer- 

 tainly been diminished. 



Again, the mountainous character of the region in question has not been 

 taken into consideration by Arago. In a country whei'e there are differences 

 of level of several thousand feet, it is evident that we may have very different 

 temperatures in different but closely adjacent regions. As long as it is not 

 known at what altitudes the plants in question respectively grew and flour- 

 ished, we have no right to draw any inferences as to the mean temperature 

 of the region. This is more especially true, in this case, when reasoning 

 in reference to a country the instrumental records of whose climate are 

 so imperfect as were confessedly those of Palestine at the time of Arago's 

 writing. 



Again, it does not appear to be by any means true that the date-palm 

 is limited to a temperature of about 21°. On the contrary, this tree seems 

 able to bear very considerable vicissitudes of climate. According to Fischer, 

 who has published an elaborate monograph on the date-palm,* it appears 

 that its cultivation is successfully cari'ied on in regions emljraced between 

 the isothermals of 16° and 30°, and that there is, in fact, no heat known on 

 the earth too great for it to thrive in.f 



It is safe to assert, therefore, that no attention whatever need be paid to 

 the statement of Arago that the temjjerature of Palestine has undergone no 

 change within the past 3,300 years. 



The history of the culture of the date-palm appears to furnish some evi- 

 dence of a deterioration of tlie climate along the northern limits of its range, 

 where, and where only, we could expect to find proof of a change, if such 

 had really taken place. Fischer cites several instances of localities where this 

 tree was once cultivated and where it no longer thrives. As an examjile of 

 this, Seistan % may be mentioned, a province on the borders of Persia and 



* Die Dattelpalnie, ilire geographisclie Verbreitung uml rultuiliistorisclie Bedeutung. Vou Tlieobald Fischer. 

 Ergiinzun^slieft to Peteiniann's Mittheilungen, No. 64 (188]). 



t " We may therefore assume that the higliest known mean teniperatui-es are perfectly suitable for it [tlie 

 date-palm] if otlier necessary conditions are fultilleJ, and that it thrives admirably in the hottest region of the 

 world, namely that enclosed within the isothermal line of 3n°. Its limits lie, then, between the isothermals of 

 16° and 30° C, and the mean annual temperatures of 15°.6 and 2S°.5 C." — 1. c, p. 53. 



X Also spelt .Sedjestau and SeJschestan. 



