10 FOREST INFLUENCES. 



scanty, and further cultivation will be necessary to gather a fuller 

 harvest and then to set clear the many comx^licated questions connected 

 with this inquiry. 



Meanwhile a thorough beginning with a view to settle the question by 

 scientific methods and careful systematic measurements and observa- 

 tions has been made in Europe, wliere the existence of well-established 

 forest administrations, manned with trained observers, has rendered 

 practi<*able the institution of such work on an extensive scale — the only 

 one which can yield adequate results. Notably the observations made 

 at the duplicate stations in Prussia, and recorded for fourteen succes- 

 sive years, furnish reliable material for the discussion at least of the 

 relation of forest cover to meteorological j)henomena, and from these 

 in time the nature and extent of any influence upon the climate, if such 

 exists, may be determined. 



Prof. M. W. Harrington, now Chief of the Weather Bureau, has, in 

 the following pages, compiled these and other observations, and in an 

 ingenious manner has compressed them iuto graphic illustrations, which 

 readily convey the results to the reader. While an attempt has been 

 made to discuss the problems and records in popular form, the student 

 of forest meteorological problems will find not less useful the clear and 

 unbiased statements of what these problems involve and what the 

 records do and do not show. 



It may be proper to call attention to and accentuate the fact that the 

 question of practical importance is not so much as to the efl'ects upon the 

 general climate, but as to the local modification of climatic conditions 

 which a forest area may produce. 



It can not be too strongly impressed upon those who disclaim any 

 influence of forest cover on climate, because the cosmic causes by 

 which this is produced are immeasurably greater, that there are two 

 classes of climate always to be considered separately, namely, the gen- 

 eral climate and the local climate. The latter is of most importance to 

 us, and alone can be modified by small causes. We modify it by building 

 a house around us, thus altering the temperature and moisture conditions 

 of the atmosphere so inclosed ; but the question is, whether we can alter 

 these conditions on a larger scale by such means as alternating forest 

 areas and fields or by large bodies of forest. We are not so much con- 

 cerned as to whether the total rainfall over the continent is increased, 

 but whether the distribution of precipitation in time and quantity over 

 and near a forest area is influenced by its existence; whether we or 

 our crops feel its absence or presence in our immediate neighborhood; 

 whether the protection it seems to afford and the changes it seems to 

 produce in the meteorological phenomena are or are not real and of 

 sufficient magnitude to influence our forest policy. 



We would here call special attention to the memoir of Prof. Cleve- 

 land Abbe, contained in this bulletin, from which the difficulty of ob- 

 taining accurate records of rainfall with the gauges iu general use is 



