302 DRAINAGE OF HOLLAND. 



Years afterwards others acted on Trevithick's drainage 

 ideas, and Harvey and Co. built Cornish pumping engines 

 with steam-cylinders 112 inches in diameter, similar 

 in principle to the Dolcoath engine 1 of 1816, which 

 effectually drained the Haarlem lake. 



The Ehine during 100 years, in its passage through 

 the low flat lands, had by deposit raised the level of 

 its waters 5 feet, threatening to overflow the embank- 

 ments and drown the surrounding country, that to a 

 large extent was at a lower level than the river. All 

 drainage from such land had to be pumped over the 

 river bank, in many places 10 feet above the cultivated 

 surface. Windmills had been used as pumping power, 

 and a company had contemplated laying out 700, OOO/. 

 in windmills and canals for drainage. 



If the surface water averaged 18 inches in depth 

 yearly, Trevithick could by steam-engines drain an acre 

 of land by the consumption of a bushel of coal yearly. 

 Four engines with cylinder of 63 inches in diameter 

 would drain 160,000 acres, and four smaller engines in 

 barges with suitable apparatus were to cut canals and 

 construct embankments. The deposit of a hundred years 

 was also to be removed, and the Rhine deepened 6 feet 

 for a breadth of 1000 yards, and a length of 50 or 60 

 miles, by steam-dredgers, as used twenty years before 

 in deepening the Thames, 2 to be fixed in iron ships of a 

 thousand tons burthen. The cost of dredging from the 

 bed of the river into a barge would be Id. per ton ; but 

 this would be more than repaid by making with it an 

 embankment, enclosing, the Zuyder Zee, which would 

 then in its turn be drained and made pasture land. 



Before leaving for America he had reported on the 

 best means of improving St. Ives Bay. 3 Hayle Harbour 



1 See vol. ii., p. 168. 2 See vol. i., p. 243. 3 See vol. i., p. 343. 



