THE FOREST AS A CONDITION. 69 



growth is at least practically prevented by climatic 

 conditions, — although the Hmits are by no means 

 known, — and hence no expectation can be had of 

 utilizing this influence in these conditions. 



Again, since undoubtedly the forest influence 

 on surroundings, as far as climatic factors are con- 

 cerned, can extend only to a limited distance, the 

 most effective result must be secured by alterna- 

 tions of forest cover and open land, hence the dis- 

 tribution of these two conditions is of as much 

 importance as the relative size of the parcels. 



Without going into the detail of the difference 

 of meteorological conditions that may exist in the 

 forest and the adjoining open country, it may be 

 briefly stated that the tendency of a forest cover 

 is to reduce extremes of high and low temperature 

 in about the same manner as does a sheet of water, 

 and this effect is most noticeable in the hot months. 

 But whether and how far this temperature differ- 

 ence is felt outside is not as yet determined. Nor 

 do we know much regarding the important influence 

 on the moisture conditions of the air and on the 

 rainfall. The tendency of a forest growth would 

 be, on account of its cooling effect, to keep the air 

 within and to some extent above it nearer satura- 

 tion, and as a consequence it might occur that 

 moisture-bearing currents passing over would pre- 

 cipitate their moisture more readily above or near 

 the forest growth. Whether they do is still doubt- 

 ful, and indeed, to make an appreciable difference 



