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CHAP. XVI.



DESCRIPTION OF PLATE XI.





	Exhibiting a machine for a descending trade, in which the whole of the water is saved, while the trade descends; yet should it be found necessary, by a further extension of the canal, to form the apparatus for an alternate trade, the water tubs may be applied



	In the first case of a descending trade, there is but one pit, which must be thirty feet diameter, a capacity sufficient to suffer two boats to pass; over the pit a building must be erected, to cover and support the works; in the center of which a drum-wheel of one diameter is placed. On each side of the drum, two chains and a cage to receive to boat is suspended; which cage will move alternately between the upper and lower canals; on the end of the upper canal, and on the side of the pit, there are two gates, balanced so as to rise perpendicular, as at A and B; and opposite the gates, parallel to the canal, two lock carriages, C and D, worked by rack and pinion, moving on iron rails; which carriages are constructed with one end open, and of a size to receive the cage and boat.



	When the lock carriage is moved forwards it sits close to the end of the canal in a groove; and the gate being opened, the water of the canal fills the carriage, which enable the man to float his boat in the cage; after which. the gate being shut, and a valve opened in the hind art of the carriage, below C S, to discharge the water, the carriage is run back and leaves the boat suspended over the pit; during this operation, the man below having placed an empty boat in the lower cage, the two boats are now ready to pass, the loaded one descending, raising that which is empty; and at the same time, by a crank movement taken off the end of the drum, three pumps are put in motion; and they raise the water, which was discharged from the lock-carriage, into a side pond, about twelve feet high, into the upper canal; by which the whole is saved. The empty boat having ascended, the second lock-carriage is run forward, and the gate of the canal being opened, the water filling the carriage, will float the boat into the upper canal; another for the purpose of descending, it then moved into the cage, and so on alternately.



	To regulate this machine, the centrifugal fans are applied, as in the other apparatus; but the balance-chains will be of no consequence, as the loaded boat descending will be sufficient to raise the weight of pendent chain, if the depth s not more than on hundred feet, also work the pumps and raise the empty boat; four tons descending would also raise three, by casting the pumps out of gear by the lever E, so that some alternate trade might be performed.



	But should the future extension produce an alternate trade, the pits and tubs may be added to this apparatus, converting it to a double machine; for a return state, this machine would transfer two boats in about eight minutes; consequently, in the descending trade, about three hundred and sixty tons might descend, returning the empty boats, in twelve hours. In the alternate trade, twice above quantity would be performed by raising loaded boats at the several moments



	Its expense for the descending trade one hundred feet deep, 

		about							L. 2,500    0    0

									    3,500    0    0

									    ___________

									    6,000    0    0

Which is about half the expense of locks.