824 M. Arago on the Therrnometrkal State 



thematically inoperative, or, at most, their influence is so minute 

 that it is not indicated by the mo^ delicate instruments. For 

 the explanation of the changes of climates, then, there only re^ 

 mains to us, either the local circumstances, or some alteration in 

 tljc heating or illuminating power of the sun. But of these two 

 causes, we may continue to reject the last. And thus, in fact, all 

 the changes would come to be attributed to agricultural opera- 

 tions, to the clearing of plains and mountains from wood, the 

 draining of morasses, &c. &c. ; provided we succeed in proving, 

 that the climate has neither become hotter or colder in a spot, 

 the physical aspect of which has not sensibly varied in a long 

 course of ages. 



Thus, at one swoop, to confine, for the whole earth, the va- 

 riations of climates, past and future, within the limits of the 

 naturally very narrow influences which the labour of man can 

 efi^ect, would be a meteorological result of the very last import- 

 ance. We shall therefore, we trust, be pardoned, for the mi- 

 nute details into which we are about to enter. A great number 

 of them, we are anxious to declare, have been brought together in 

 the works of M. Schouw, a Danish traveller, alike distinguished 

 for his botanical and his meteorological labours. 



VIII. JTie Mean Temperature of Palestine does not appear to Jiave 

 changed since the time of Moses. 



That the palm-tree may bear fruit, or, more accurately, that 

 the date may ripen, a certain degree of mean temperature is, at 

 the least, required. On the other hand, the vine cannot be culti- 

 vated wdth profit ; it ceases to aflbrd fruit fit for the manufac- 

 ture of wine, so soon as this same mean temperature exceeds a 

 point of the thermometer equally determinate. But the lowest^ 

 thermometrical limit for the date, differs but very little from the 

 higliest thermometrical limit for the vine ; if, then, we find, that 

 at two different epochs, the date and the grape ripened simul- 

 taneously in any given place, we may affirm that, in the inter- 

 val, the climate has not perceptibly changed. Let us now see 

 how far this influence is supported by facts. 



Jericho was called the town of palm-trees. The Bible alludes 

 to the palm-trees of Deborah, situated between Rama and 

 Bethel, of those skirting the banks of the Jordan, &c. The 



