ciduous trees that are entwined with much ivy 

 seem to distil the greatest quantity. Ivy leaves are 

 smooth, and thick, and cold, and therefore condense 

 very fast ; and besides, evergreens imbibe very little. 

 These facts may furnish the intelligent with hints 

 concerning what sorts of trees they should plant 

 round small ponds that they would wish to be per- 

 ennial ; and show them how advantageous some 

 trees are in preference to others. 



Trees perspire profusely, condense largely, and 

 check evaporation so much, that woods are always 

 moist: no wonder therefore that they contribute 

 much to pools and streams. 



That trees are great promoters of lakes and 

 rivers appears from a well known fact in North 

 America ; for, since the woods and forests have 

 been grubbed and cleared, all bodies of water are 

 much diminished ; so that some streams, that were 

 very considerable a century ago, will not now drive 

 a common mill."^ Besides, most woodlands, forests, 

 and chases, with us abound with pools and mo- 

 rasses ; no doubt for the reason given above. 



To a thinking mind few phenomena are more 

 strange than the state of little ponds on the sum- 

 mits 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 



* Vide Kalm's " Travels in North America." 

 67 



