Page:The Canal System of England.djvu/50

 trough ascending as the other descends, the latter containing 6 inches greater depth of water, its descent being thus facilitated.

The great objection to such lifts is their first outlay and the cost of maintenance; the Anderton lift with troughs 75 feet by 14·5 feet cost £5,000, and the maintenance averages £500 per annum. The great advantage of this method, however, is the great saving of time and water and as this latter is a matter of the most vital importance in a district where the water supply is poor, this method is one which bids fair to be adopted, in order to effect the changes of level in future canal construction.

The study of the economy of the different systems for effecting changes of level points to the lock system as the cheapest. Assuming that 30 hydraulic lifts could be made to take the place of the proposed locks on the route from South Staffordshire to London, and that they could be worked @ 0·20d. per ton (the figure given by Mr. Saner who had over 10 years experience of the Anderton lift), this would represent 6d. per ton for lifts to London as against 3d. per ton for pumping. The lift system thereby differing from the lock system also requires the attention of skilled men, entailing extra expense. Whilst it may be said that locks are wasteful of water, and that this waste must be made up by pumping, there is this advantage over a mechanical arrangement, that in times of large rainfall no cost is incurred in supply. Locks are