164 ESTFLUElSrCE OF THE FOEEST ON TEMPERATURE. 



terror over the land from Avignon to tlie Bouches-du-Rlione, 

 tlience to Marseilles, and then extended its ravages, diminished 

 indeed by a long career which had partially exhausted its force, 

 over the whole maritime frontier. The people thought this wind 

 a curse sent of God. They raised altars to it and offered sacri- 

 fices to appease its rage." It seems, however, that this plague 

 was less destructive than at present, until the close of the sixteenth 

 century, when further clearings had removed most of the re- 

 maining barriers to its course. Up to that time, the northwest 

 wind appears not to have attained to the maximum of specific 

 effect which now characterizes it as a local phenomenon. Ex- 

 tensive districts, from which the rigor of the seasons has now 

 banished valuable crops, were not then exposed to the loss of their 

 harvests by tempests, cold or drought. The deterioration was 

 rapid in its progress. Under the Consulate, the clearings had 

 exerted so injurious an effect upon the chmate, that the cultivation 

 of the olive had retreated several leagues, and since the winters 

 and springs of 1820 and 1836, tliis branch of rural industry has 

 been abandoned in a great number of locahties where it was ad- 

 vantageously pursued before. The orange now flourishes only at 

 a few sheltered points of the coast, and it is threatened even at 

 Hyeres, where the clearing of the hills near the town has proved 

 very prejudicial to this valuable tree. 



Marchand informs us that, since the felling of the woods, late 

 spring frosts are more frequent in many locahties north of the 

 Alps ; that fruit trees thrive no longer, and that it is difficult 

 even to raise young fruit trees.* 



Influence of the Forest, considered as Inorga/nic Matter, on 

 Ternperature. 



The evaporation of fluids, and the condensation and expansion 

 of vapors and gases, are attended with changes of temperature ; 



* U(^&r die EnUcaldung der Oebirge, p. 28. 



Interesting facts and observations on this point will be found in the valuable 

 Report on the Effects of tJie Destruction of the Forests in Wisconsin, by Lapham 

 and others, pp. 6, 18, 20. 



