460 



Mr. Downing on the Drainage of Haarlem Lake. 



The sale of the land will realize about £400,000, and the land-tax of 7s. id. 

 per acre, being capitalized, represents a nearly equal sum ; moreover, the 

 annual cost of the eastern dykes, set down at £5000 a year, now ceases, and 

 in the profit to the State we cannot omit the saving thus effected. 



The horizontal hne represents time, each equidistant vertical being separated 

 a space taken conventionally as equal to one month. The verticals represent 

 depth from original surface of Lake to surface as lowered at that date, in feet 

 or metres, according as we use either of the comparative scales given, that on 

 the left being metres, and on the right, feet. By joining the feet of these verti- 

 cals we get an irregular line, from which we may obtain the depth pumped out 

 at any intermediate period. 



