Pumping Stations. 143 



raised 900,000,000 tons. The time the pumps were actually at work 

 was nineteen and a half months, frequent delays occurring from the 

 valves becoming choked with silt and other causes. In the winter 

 season the rainfall, with the absence of evaporation, gained upon the 

 power of the engines. The general average lowering of the surface 

 was at the rate of about 4 inches per month, every inch in depth 

 giving 4,000,000 tons. 



The dyke and canal were finally completed in 1848, and pumping 

 began with the Leeghwater, and with the other engines in the spring 

 of the following year. The lake was laid dry in 1852. The works 

 for fitting the bed of the lake for cultivation consisted in making 

 main canals 80 feet wide along the centre from north to south and 

 from east to west, terminating at their respective ends at the three 

 pumping stations. Four smaller canals parallel with the others were 

 made lengthways, and six across the lake. The subdivisions con- 

 tained fifty acres each. The length of the large canals was 18*63 

 miles ; of the smaller, 93*15 miles. The total length of the canals 

 and ditches was 750 miles. There were also made 122 miles of 

 roads and sixty-five bridges. The total area of the polder to the 

 encircling canal is 41,648 acres, of which 301 1 acres, or about 6| per 

 cent., are occupied by roads and main waterways. The estimated 

 expenditure at the commencement of the operations was 687,500/. 

 The total amount actually expended was 781,500/. — at the rate of 

 16*57/ per acre of available land, out of which the dyke and canal 

 cost 161,527/; the engines, boilers, and pumps, 71,216/; and 

 buildings for same, 50,615/ Taking the power in water lifted at 

 1037 horse-power, this is equal to 48*23/ for buildings; (>^*(>(iL 

 for machinexy; together, 116*89/ P^^ horse-power. The net cost 

 after sale of the lands, exclusive of interest and commission, was 

 86,042/, for which 41,648 acres were added to the taxable resources 

 of the country, and provision made for the maintenance of a large 

 population, now amounting to over 12,000. The first public sale of 

 the land took place in 1853. The prices realised ranged from 25/, 

 the average over the whole polder being about 16/ an acre. 



The average rainfall on the polder for the ten years ending 1872 

 was 31*267 inches. The time the pumps were working was 5584! 

 hours, divided as follows : — 



Rainfall. Hours 



inches. pumps working. 



First four months 7*472 2254! 



Second „ 10*503 398! 



Third ,, 13*292 2932 



