164 THE NATUKAL HISTORY 



considerable a century ago, will not now drive a common 

 mill. 1 Besides, most woodlands, forests, and chases, with us 

 abound with pools and morasses ; no doubt for the reason 

 given above. 



To a thinking mind few phenomena are more strange than 

 the state of little ponds on the summits of chalk-hills, many of 

 which are never dry in the most trying droughts of summer. 

 On chalk-hills I say, because in many rocky and gravelly soils 

 springs usually break out pretty high on the sides of elevated 

 grounds and mountains ; but no person acquainted with chalky 

 districts will allow that they ever saw springs in such a soil but 

 in vallies and bottoms, since the waters of so pervious a stratum 

 as chalk all lie on one dead level, as well-diggers have assured 

 me again and again. 



Now we have many such little round ponds in this district ; 

 and one in particular on our sheep-down, three hundred feet 

 above my house ; which, though never above three feet deep in 

 the middle, and not more than thirty feet in diameter, and 

 containing perhaps not more than two or three hundred hogs- 

 heads of water, yet never is known to fail, though it affords 

 drink for three hundred or four hundred sheep, and for at least 

 twenty head of large cattle beside. This pond, it is true, is 

 over-hung with two moderate beeches, 2 that, doubtless, at times 

 afford it much supply : but then we have others as small, that, 

 without the aid of trees, and in spite of evaporation from sun 

 and wind, and perpetual 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 Mat/ 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 counter- balance the waste of the day ; without which the 

 cattle alone must soon exhaust them ? And here it will be 

 necessary to enter more minutely into the cause. Dr. Hales, in 



1 Vide Kalnfs Travels to North- America. 



2 [One of the identical beeches here referred to was, for at least fifty or sixty years, 

 leaning at a considerable angle over the pond, and has fallen prone into the water 

 only very recently. It was not a large tree ; it had become somewhat decayed, but 

 retained its leafy head until it fell uprooted. Bell.} 



