138 GEOLOGICAL SURVEY OF NEW JERSEY. 



the area of forests in all of northern New Jersey is as great as it 

 was fifty years ago, and the quality of the timber has been 

 steadily improving for at least forty years. It is therefore clear 

 that if the streams are falling off it is not due to deforestation. 

 There is no competent evidence, based on careful measurement, 

 that there has been any important change in the streams, except- 

 ing what may be accounted for by artificial diversions of their 

 waters, or by the fact shown by the rain-fall records that pro- 

 tracted droughts have been more frequent during the last 

 quarter-century than they were during the previous quarter. 



While popular opinion is clearly wrong in this case, therefore 

 we believe it is true that by reason of deforestation streams 

 become more fluctuating and subject to longer periods of 

 extreme low water. This would be quite sufficient to account 

 for a popular impression that there is a shrinkage in the run-off. 

 It is quite impossible to determine, except by exact measure- 

 ments, any change in the total run-off of the streams during the 

 year. More protracted periods of low water would be sufficient 

 to account for many of the phenomena, such as the shrinkage 

 in water-power, etc., which are so often adduced as proof that 

 deforestation increases evaporation. The large volume of water 

 which may have been discharged in floods during the wet season 

 has been lost sight of, as it is of little use for power, and its 

 volume cannot be estimated by the eye. 



The conclusions which we have reached are generally similar 

 to those which have been set forth by Antoine C. Becquerel, a 

 member of the French Academy of Science, who devoted most 

 of a long life-time to the subject, and who had at his disposal the 

 best European data. * 



He points out the injurious effect upon springs and water- 

 courses due to deforestation, but says : "It cannot be said that 

 this diminution is caused by a less annual rain-fall or a greater 

 evaporation of rain-water. " 



In his opinion, the real effect is due to a more irregular and 

 flashy discharge of the stream waters. His conclusions are 

 altogether so conservative and embody the results of so much 

 experience and study of European conditions, that his paper is 

 especially commended to the reader's attention. 



* Memoirs upon Forests and their Climatic Influence ; Atlas Meteorologique de L' Observatoire Im- 

 perial, 1867 A full translation appears in Report upon Fo estry, byF. B. Hough, United States Depart- 

 ment of Agriculture, 1877. 



