7, YORKSHIRE. 171 



would lad through ages ; and although the 

 expence in the firft inftance would be fonic- 

 thing more than that ot loofc {tones, its dura- 

 bility would in the end doublv repay it. 

 Even the Wold ponds, which have been 

 made fifteen or twenty years, are many of 

 them beginning to fail, and will in a few 

 years require to be frefli coated ; whereas a 

 pond properly paved w^ould, in all human 

 probability, remain perfedl for at leaft a 

 century. 



There would be an advantage of a paved 

 pond which may not ftrike every one. The 

 clay and its coverings, while the pond is fil- 

 led with ai',\ appear to be a firm folid mafs, 

 which would require a great power to dj- 

 fturb it. But the pond being filled with 

 •zc-^/^r the texture of the clay is changed, and 

 the relative gravity of all the covering ma- 

 terials confiderably altered. They no longer 

 adhere to the bottom with the fame firmnefs, 

 nor in fadt lie upon it with the fame weight, 

 they did before the water v/as let in. For if 

 inftead of fi:one the clay had been covered 

 with blocks of wood (for inftance), whofe 

 fpecific gravity is Icfs than that of water, 



.they 



