OF NATURAL PHILOSOPHY. 61 



we to say 100 millions instead of 70, we should pro- 

 bably be nearer the truth. 



(55.) The powers of wind and water, which we are 

 constantly impressing into our service, can scarcely 

 be called latent or hidden, yet it is not fully con- 

 sidered, in general, what they do effect for us. 

 Those who would judge of what advantage may be 

 taken of the wind, for example, even on land (not 

 to speak of navigation), may turn their eyes on Hol- 

 land. A great portion of the most valuable and 

 populous tract of this country lies much below the 

 level of the sea, and is only preserved from inun- 

 undation by the maintenance of embankments. 

 Though these suffice to keep out the abrupt in- 

 flux of the ocean, they cannot oppose that law 

 of nature, by Avhich fluids, in seeking their level, 

 insinuate themselves through the pores and subter- 

 raneous channels of a loose sandy soil, and keep 

 the country in a constant state of infiltration 

 from below upwards. To counteract this tendency, 

 as well as to get rid of the rain water, which has no 

 natural outlet, pumps worked by windmills are estab- 

 lished in great numbers, on the dams and embank- 

 ments, which pour out the water, as from a leaky ship, 

 and in effect preserve the country from submersion, 

 by taking advantage of every wind that blows. To 

 drain the Haarlem lake * would seem a hopeless 

 project to any speculators but those who had the 

 steam-engine at their command, or had learnt in 



* Its surface is about 40,000 acres, and medium depth 

 about 20 feet. It was proposed to drain it by running em- 

 bankments across it, and thus cutting it up into more manage- 

 able portions to be drained by windmills. 



