121 



INCREASE IN OUR AREAS OF EVAPORATION. 



Our areas of evaporation are becoming larger and our areas of 

 water-retention are being correspondingly reduced. What this means 

 may be easily understood when we remember that from a mile square 

 of water surface there would evaporate during the month of July on 

 the average 3,339,304 gallons of water. Our larger, as well as our 

 smaller, streams, are however during the warmer months of the year 

 reduced in evaporating area until but a small portion of the stream 

 bed is covered with water. The thirsty air makes, therefore, increas- 

 ing demands upon the moisture in the agricultural areas, until the 

 drought jeopardizes the very life of the growing crops; notwithstand- 

 ing the fact that as much rain falls as formerly. There can be no 

 doubt but that one reason for this great loss'of water from the State's 

 surface is due to the removal of forest covering, which changes the 

 condition from a water-retaining surface to an evaporating surface. 

 Even granting that land in crops is shaded and hence to a certain ex- 

 tent protected from the direct rays of the sun, it is well known that 

 from such ground the rate of evaporation is much larger than from a 

 forest covered area. 



The above statements might be put in a practical form by taking 

 adjacent parts of the counties of Dauphin and Perry. The Susque- 

 hanna river separates these counties, and the Juniata runs through 

 the northeastern portion of Perry. The aggregate surface area of 

 these two stream beds from Georgetown to Kockvilleand from Middle- 

 town to Juniata bridge, would probably be not less than thirty-one 

 miles. If one square mile during a summer month is capable of evap- 

 orating 3,339,304 gallons of water, then from this thirty-one miles 

 there should be evaporated 103,518,424 gallons of water. If, however, 

 by reason of low water, one-half of the stream bed becomes dry, then 

 the evaporation is reduced to 51,759,212 gallons. In other words, 

 the air passing over the adjacent regions is so much less near the 

 point of saturation and therefore the more eager to absorb moisture 

 from the cultivated surfaces. 



Or we may put the proposition in another form. Air which would 

 have the whole of the above quantity of water (103,518,424 gallons) 

 in the form of vapor would be much more likely to deposit a portion of 

 it in the form of dew, which to a certain extent is directly or indirectly 

 available for the support of plant life, even if it did not occasionally 

 take the form of showers which would refresh the whole plant through 

 the roots. 



From all of the facts, available now, it would appear that the de- 

 nuded condition of so much of our ground is becoming a menace to our 

 general prosperity. If this is so then it is a duty of the hour to an- 

 ticipate and prevent it, by encouraging the renewal of timber on lands 



