ON THE RAINFALL. 299 



the amount of rainfall all the world over has not been diminished rather 

 than increased since was issued the fiat : Let the earth bring forth 

 grass upon the earth — the herb yielding seed, and the fruit tree 

 yielding fruit after its kind whose seed is in itself. 



I have quoted the statements of Herr Wex in regard to the local 

 effects of forests on the rainfall, given in his treatise on the " Diminu- 

 tion of Water in Streams and Rivers, with the increase at the same 

 time of occasional inundations in low-lying agricultural districts. " 



The Commission appointed by the Academy of Science at Vienna, 

 appointed to consider that treatise and to report, reported in regard 

 to the effect of forests on the rainfall as follows : — " The influence of 

 forests on the quantity of the rainfall is a subject which has engaged 

 the attention of many naturalists. From many different points of 

 view has this influence been discussed, the discussion being founded 

 partly on theoretical considerations, partly on the altered climatal 

 conditions of country in which forests have been destroyed. 



"In connection with theoretical considerations it has been ex- 

 tensively maintained that forests arrest the floating clouds, as do 

 mountain ranges opposed to a current of clouds, and like these occa- 

 sion a condensation of moisture ; and further that by the relatively 

 lower temperature prevailing in a forest than in the open country, thus 

 occasion a precipitation of that moisture in the form of rain ; and in 

 reference to this point more especially has Dr Berger in Frankfort 

 devoted attention to the difference in favour of rainfall in the 

 temperature and condition of moisture in the forest, in comparison 

 with these in the open country. 



" It is on the whole probable that some such influence is produced 

 by forests ; but perhaps on the one hand the importance of this in- 

 fluence has been over-estimated ; and on the other hand there is a lack 

 of direct and decisive proof as to the effect ; as the pluviometrical 

 observations made for this purpose in stations within and outside the 

 forests extend over too short periods, and to some extent have been 

 made in conditions or circumstances which do not admit of strict 

 comparison, such as the difference in condition at different eleva- 

 tions, inclinations, and exposures in difierent directions, &c. 



" From the great importance, in the interest of agi-icultui-e, of the 

 alleged diminution in the rainfall, the Scottish Meteorological Society 

 decided, in 1859, at the request of their president, the Marquis of 

 Tweeddale, to offer a prize for an essay on the question, Whether any 

 change had occurred in the quantity of rainfall in the west of Europe. 



