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subsequently, by the failure of its banks, to the Marshland district which 
has a separate drainage. It is not necessary here to narrate the series of 
unsuccessful attempts to stay the progress of the flood. In the end, Mr. 
Hawkshaw succeeded in forming a dam which has kept out the tide by con- 
structing twoparallel walls across the drain, consisting of close piles, extended 
gradually from each side towards the centre where an opening of ninety 
feet was left. Across this opening twin piles were driven, at distances of 
about seven feet from pair to pair, and with a space of eight and a half 
inches between the piles of each pair. In the groove between the twin piles 
massive panels were dropped at the ebb, when the flood on the lands was 
at its lowest. The panels were sufficiently strong to prevent the ingress 
of the tide, until by filling up the space between the two rows of piling 
w ith puddle, and dropping barge-loads of chalk and stone against their 
interior and seaward faces, the temporary dam was converted into an 
impervious and durable embankment. It now remained to draw off the 
waters from the flooded land, and to provide for the future exit of the 
drainage waters of the Middle Level, which otherwise in winter would have 
endangered the rescued lands as much as the tide had done before. For 
this purpose, Mr. Hawkshaw has adopted six immense iron syphons, the 
number of which is to be increased to fifteen. Each syphon consists of a 
tube three feet six inches in diameter and 150 feet long, which rising from 
the lowest level on the landward face of the embankment, bend over 
its crest and dip down to the foot on the seaward face. They have valves 
at each end which permit the flow of the water from the drain towards 
the sea whenever the tide has fallen, so that the level of the water in the 
drain is above that outside ; but prevent its reflux on the return of the 
tide. A ten horse-power steam-engine and air-pumps are employed to 
exhaust the air from the syphons, both that originally in them and that 
continually disengaged from the water. About 50,000 gallons of water 
per minute are said to be discharged by the six syphons already con- 
structed. 
Mr. Thorold has suggested the employment in future, in works of this 
kind, of a duplicate sluice at the back of the sea-sluice, for the purpose of 
keeping up a head of water, at an intermediate height, between the two 
sluices, when the sea-sluice is closed by the tide ; so that the hydrostatic 
pressure may be distributed over twice as many supports as hitherto. 
Dr. Grimaldi has introduced a form of boiler, similar in many respects 
to the old multitubular, but in which the system of tubes is maintained in 
slow revolution about the axis of the boiler. The generation of steam is 
more effective than with fixed heating surfaces, and the boiler space for a 
given quantity of steam may be reduced one-half. A small engine has been 
constructed in America, in which the boiler considered as a reservoir of steam 
is dispensed with. The steam is generated at the instant it is required in a 
small vessel thirteen inches diameter by thirty inches long, into which the 
feed water, previously heated by the exhaust steam, is admitted in measured 
quantities and in the form of spray. This spray impinging on highly 
heated metallic surfaces, flashes into steam and is superheated. No doubt 
on this plan some of the sources of danger and waste which exist in 
ordinary steam-engines are avoided, but a most serious defect is probably 
