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direction of working lifts for subway traffic, both vehioularand passenger. In many cases where the construction of abridge to convey traffic over a river is objectionable, a subter-ranean communication bas been difficult to make, owing to theapproaches to the subway being impracticable. Mr. Greatheadand Sir William Armstrong , Mitchell & Co., have given muchattention to the question of providing hydraulic lifts, whichwould enable the long and expensive approaches to a subwayto be dispensed with, and which would at the same time meetuninterruptedly the demands of a large vehicular traffic.
An example of this is shown by fig. 15, -which represents theArrangement of hydraulic lifts proposed to be placed on TowerHill. There are two series of cages or compartments (whichare well lighted), so arranged as to admit of free ingress andegress of the traffic going in both directions. One series is forlowering the traffic going southwards through the subway, andthe other is for raising the traffic coming northwards from the
Fig. 15.
subway. Eaeh of the compartments is of such a size as to takeeither the largest vehicle and four horses, or a trainway car andhorses, or two smaller vehicles and their horses. The workingof the lift is as follows:—A vehicle arriving would pass into,say, the first of these large compartments, and be loweredimmediately to the roadway below. The vehicle followingwould pass into the next compartment and be lowered. Bythe time the last of the series of lifts or compartments hadgone down, the first would be back again at the surface for a