70 



nature to convince the most incredulous as to the duty of the state foresters to seek 

 without further delay for such remedies as the situation demands, so great is the actual 

 peril." 



A most valuable paper bearing on this point was read at the Cincinnati Congress, by 

 the Hon. V. Colvin, Superintendent N. Y. S. Adirondack Survey. I wrote to Washington 

 for this paper, but it was not in print. I can therefore only give my readers the abstract 

 given by the Forestry Congress Commissioners sent from Ontario : — 



" The influence of forests upon the water supply of any given drainage area is 

 directly proportional to the rainfall, and it is from the standpoint of evaporation and 

 rainfall that the effect of forests must be considered. 



" The data for the investigation must be searched for in the east, where the des- 

 truction of forests has been great. Here, rather than on the frontiers of civilization, we 

 should look for traces of climatic change, if the destruction of forests lead to any change. 



" The records of the United States Signal Service of the mean monthly precipitation 

 in this country for many years had been searched by the lecturer for statistical informa- 

 tion on this subject, and he had based upon these records a series of computations which 

 showed where the greatest irregularities in the monthly rainfall occurred. 



" These differences were presented in tabular form, and showed a favourable uniform 

 monthly precipitation of rain in the middle Eastern States. Here it is known that the 

 approximate limit of safety of forest-cutting has been reached, as torrential action began 

 to show itself in sections where much timber had been cut away. 



" The topography of the country was shown to have a most important bearing upon 

 the quantity effect of forests upon the rainfall ; the mountain ranges, when forest-covered 

 and extending across the path of the south winds, acting as powerful condensers of 

 moisture. The way in which limbs of trees entangle and kill the wind, to which a house 

 or block of houses forms hardly any obstacle, was explained in an interesting manner, 

 and was shown to be dependent on the angle of incidence. 



"The true relationship of atmospheric electricity to rainfall was traced through the 

 reactions of the correlated force, so often incorrectly termed "latent heat." The limbs, 

 boughs and leaves of the forest were (when considered mechanically) natural machinery 

 most wonderfully adapted to the purpose of grasping upon the atmosphere, and thus 

 causing those dynamic changes which induce precipitation of moisture. 



" The forests were, in fact, most singularly complicated condensers, and performed 

 their peculiar office in the atmosphere far better than the most skilfully contrived alembic 

 of the chemist. 



" Forests were shown to be essential to a uniform rainfall when existing in the 

 proper localities, as determined by the great local meteorological laws. 



" A knowledge of the path of storms in any locality, and of the topography — the 

 elevations and depressions, the rivers, marshes and lakes — was shown to be essential to 

 any exact estimate of the limit of safety of the cutting of forests. The only way in 

 which the wide-spread knowledge necessary could be obtained would be by a general 

 system of observation by farmers and others throughout the whole country, of the great 

 facts of the local rainfall, direction of winds, etc., which could be easily done with little 

 trouble. 



"With these observations, and an accurate system of topographical and forest maps 

 (which every State should have made), it would be possible to make close estimates as to 

 where forests must be preserved, where replanted and where they might be safely cut. 

 The lecturer told of his personal experiences on the mountain peaks of the Adirondacks 

 and the Rocky Mountains, traced the origin of rain from its evaporation by the sun's 

 rays from the sea to its condensation to cloud — and showed how Buy Ballot's law rea- 

 dily enabled meteorologists knowing the path of storms, from a mere knowledge of the 

 present direction of the wind and the area of the last high or low pressure, to determine 

 the probable maximum or minimum liable to follow, and probable change in the direction 

 of the winds ; but that the location of forests greatly modified the exact application of 



