23G DISCUSSION OF THE DESICCATION QUESTION. 



the extreme temperatures observed in January and July are becoming more 

 nearly alike from year to year."* 



The reader is in a position to appreciate the value of these astonishing 

 statements in regard to our climate, from what lias been set forth in the 

 preceding pages, in which the negative results obtained by Schott in working 

 up the records of the instrumental observations taken over the whole country 

 have been set forth. The only shadow of evidence which exists in suj^port 

 of Arago's statements as to the changes of our climate is to be found in the 

 paper of Professors Loomis and Newton, to which reference has been pre- 

 viously made.f According to them, the summers at New Haven are cooler 

 than they were at the beginning of the present century.t It is noticeable, 

 however, that these authors are inclined to ascribe this increasing coolness 

 of the summers, which they evidently regard as a local matter, to the growth 

 of a great number of trees in the streets of the city, while Arago explains 

 the same change, which he thinks he has proved to have occurred in Europe, 

 and assumes as having taken place here, to precisely the opposite cause, 

 namely, cutting down the forests. 



A very considerable amount of evidence has been collected by various 

 authors, to the same effect as that furnished by Arago in reference to Cen- 

 tral France, namely, that conditions favorable to the growth of certain plants, 

 especially the vine and the olive, have changed in the course of centuries, so 

 that they can no longer be successfully cultivated in regions where they once 

 flourished. 



It is also admitted by eminent physical geographers, that the character 

 and distribution of the ibrests in various parts of Europe, and especially in 

 the more northern countries, indicate an increase of cold. This appears to be 

 notably the case in Iceland, on the Shetland Islands, and in Lnpland, where 

 the birches are said to be dying out and are not replaced by a new growth. 



Similar statements are ma.de by many writers on the forests of Switzerland, 

 to the effect that it appears to be more and more difficult for the trees to 

 maintain themselves at high altitudes, a fact analogous to what has been 

 already stated in regard to the Himalayas and the Sierra Nevada. In the 

 case of the Swiss Alps, however, it seems to be increasing cold, rather than 

 dryness, which is bringing about the indicated result. The attention of the 



* 1. c, p. 236. 



t See ante, p. 225. 



X This evidence had not, however, been puhlished at the time Arago's volume was written. 



