350 NATURAL HISTORY 



but then we have others as small, that, 

 without the aid of trees, and in spite of 

 evaporation from sun and wind, and perpe- 

 tual consumption by cattle, yet constantly 

 maintain a moderate share of water, without 

 overflowing in the wettest seasons, as they 

 would do if supplied by springs. By my 

 journal of Mai/ 1775, it appears that " the 

 " small and even considerable ponds in the 

 " vales are now dried up, while the small 

 '* ponds on the very tops of hills are but 

 ** little affected.'' Can this difference be 

 accounted for from evaporation alone, which 

 certainly is more prevalent in bottoms ? or 

 rather have not those elevated pools some 

 unnoticed recruits, which in the night time 

 counterbalance the waste of the day; with- 

 out which the cattle alone must soon ex- 

 haust them ? And here it will be necessary 

 to enter more minutely into the cause. Dr. 

 Haies, in his vegetable Statics, advances, 

 from experiment, that " the moister the 

 " earth is, the more dew falls on it in a 

 ** night : and more than a double quantity 

 " of dew falls on a surface of water than 



