TRANSACTIONS OF THE SECTIONS. 119 
or 2 feet of the surface of the ground, and the ladles or float-boards dip 5 feet below 
the water, leaving a fuot in depth below the dip of the wheel, that the water may 
run freely to it, and to allow for the casual obstruction of weeds in the main drain, 
which, if it be sufficiently capacious and well-formed, will bring down the water to 
the engine with a descent of 3 inches in a mile. 
Suppose then the wheel to dip 5 feet below the surface of the water in the 
main drain, and that the water in the river into which this water must be raised and 
discharged has its level 5 feet above that in the drain, the wheel in such case will be 
said to have 10 feet head and dip, and ought to be made 28 or 30 feet in diameter. 
Mr. Glynn has found it practicable to throw out the water against a head of 10 feet 
with a dip of 5 feet, that is to say, 15 feet of head and dip, with a wheel of 365 feet 
in diameter, but in another engine more recently erected, he has made the wheel 
40 feet in diameter. The engine that drives this wheel is of 80-horse power, and is 
situated on the Ten-mile Bank near Littlepool, in the Isle of Ely. The largest quan- 
tity of water delivered by one engine is from Deeping Fen, near Spalding ; this fen 
contains 25,000 acres, and is drained by two engines, one of 80 and one of 60-horse 
power. 
The 80-horse engine has a wheel of 28 feet in diameter, with float-boards or ladles 
measuring 5} by 5 feet, and moving with a mean velocity of 6 feet per second; so 
that the section of the stream is 273 feet, and the quantity discharged per second 165 
cubic feet ; equal to more than 4% tons of water ina second, or about 16,200 tons of 
_ water in an hour, 
It was in 1825 that these two engines were erected, and at that time the district 
was kept in a half-cultivated state by the help of 44 windmilis, the land at times being 
wholly under water. It now grows excellent wheat, producing from four to six quar- 
ters to the acre. In many districts land has been purchased at from 101. to 20/. an 
acre, by persons who foresaw the consequences of these improvements ; they could 
now sell at from 50/, to 70/. an acre. 
__ This increase in value has arisen, not only from the land being cleared from the 
injurious effects of the water upon it, but from the improved system of cultivation 
the farmers have been enabled to adopt. 
The fen-lands in Cambridgeshire and great part of the neighbouring counties are 
formed of a rich black earth, consisting of decomposed vegetable matter, generally 
- from 6 to 10 feet thick, although in some places much thicker, resting upon a bed 
_ of blue gault containing clay, lime, and sand. i 
_ When steam-drainage was first introduced, it was the practice to pare the land and 
_ burn it, then to sow rape-seed, and to feed sheep upon the green crop, after which 
_ wheat was sown, The wheat grown upon this land had a long weak straw, easily 
_ bent and broken, carrying ears of corn of small size, and having but a weak and un- 
_ certain hold by its root in the black soil. 
Latterly however, chemistry having thrown greater light upon the operations of 
agriculture, it has been the practice to sink pits at regular distances through the 
_ black earth and to bring up the blue gault, which is spread upon the surface as ma- 
‘bure. The straw by this means, taking up an additional quantity of silex, becomes 
firm, strong, and not so tall as formerly, carrying larger and heavier corn, and the 
_ mixture of clay gives a better hold to the root, rendering the crops less liable to be 
laid by the wind and rain, whilst the produce is most luxuriant and abundant. 
On Investigations undertaken for the purpose of furnishing data for the 
Construction of Mr. Stephenson's Tubular Bridges at Conway and Menai 
Straits. By Professor E. HopGKinson. 
On a new Element of Mechanism. By Ricuarv Roserts. 
_ By this contrivance, a model of which was exhibited by Mr. Roberts, differential 
movements, for which more complicated mechanism is frequently employed, may be 
effected in a very simple manner. 
The model consisted of a steel shaft, on which were fitted loosely two brass discs, 
 @ach having a boss to keep it steady. One of the dises had on its circumference 
