76 The Drainage of Fens and Low Lands, 



Holland, advises that the angles of ingress and egress of the 

 scoops should be about equal with the mean internal and 

 external water levels. If there is any variation, it is certainly 

 better to increase the angle of egress, as this prevents useless 

 lifting of the water at the point of discharge, and more is 

 gained on the egress than is lost on the ingress side. Some 

 of the Dutch wheels, however, are constructed so that the 

 angle of egress is double that of the angle of ingress. The 

 wheels at Katwijk, which are of recent construction, are made 

 tangential to a circle concentric with the wheel, and having a 

 radius of 5*25 feet, the diameter of the wheel being 29 feet 

 6 inches. This gives the angle of ingress with the water at 

 mean level 20 degrees 30 minutes, and the angle of egress 

 42 degrees. The wheels at Podehole for the drainage of 

 Deeping Fen, the larger of which is 30 feet in diameter, have 

 scoops which incline from the radial line 25 degrees, being 

 tangential to a circle having a radius of 3*75 f^^t. If the 

 scoops were straight they would enter the water with S feet 

 dip at an angle of 29 degrees, and leave it with an angle of 

 36 degrees. The scoops are 6 feet 6 inches long ; the ends 

 for a length of 18 inches being bent back from the straight line 

 about 6 inches. 



The best average results are probably obtained from wheels 

 having an angle of ingress of 30 and of egress of 45, when 

 the water is at its mean level. 



In order to avoid the undue lifting of the water, and also 

 to facilitate the entry, wheels, both in this country and in 

 Holland, have been fitted with curved scoops made of sheet 

 iron, the rest of the wheel also being generally of iron. At 

 normal levels these wheels work well, but when the internal 

 water level alters, the convex part of the scoop strikes the 

 water, and any advantage otherwise gained is lost Wheels 

 with curved scoops should always be provided with a shuttle to 

 adjust the flow of water. The variation in the level may, to 

 a certain extent, be thus provided against Curved wheels 



