since each vehicle was subjected to the same retarding action; but it was necessary that this should be effected, as far as possible, without any complicated mechanical arrangements likely to get out of order in practice. My invention, which I call the hydrostatic brake, was one of extreme simplicity. Under ordinary circumstances the application of hydraulic power means packed pistons, water-tight stuffing- boxes, inlet and outlet valves, etc., all of which mechanical appliances were, in my plan, entirely dispensed with, and a rectangular cell of vulcanite rubber was used for transmission of the pressure.

The arrangement was as follows:-- A rectangular iron box was held by bolts passing through flanges at each end, by means of which it was secured to the underside of the carriage frame. The interior of the box was 7 1/2 in. long by 4 in. broad and 8 in. deep, and there was fitted inside it a block of wood, not unlike one of the blocks used in street paving, and having a curved lower surface fitting the tyre of the carriage wheel. This block projected downwards from the mouth of the box, and left a space of 1 1/2 in. between it and the upper closed side. Into this space was fitted a hollow rectangular chamber or box of vulcanised rubber, capable of expanding and contracting; it was attached to the wood-block on its lower surface and to the box on its upper side. There was a small pipe which connected the chamber with a continuous pipe leading to the locomotive, where the driver could turn water pressure on or off instantly whenever necessary. Each of the rubber chambers contracted by external atmospheric pressure if connected to the exhaust, and lifted the wood-block from off the wheel; but the instant that pressure was applied, each of the chambers expanded, and pressing on its wood-block forced it in contact with the wheel and retarded the motion. Thus if the wood block were 7 1/2 in. by 4 in., it presented a surface of 30 square inches, and every 10 lb. to the inch pressure on its surface was equal to 300 lb. on the wheel. The main leading pipe was always charged with water, which is non-elastic, and was permanently in communication with each of the chambers. If half a pint of water was exhausted from each chamber, the block was raised more than half an inch from the wheel, and relieved the pressure. Modifications of this simple brake have been made; but it came before its time, and was not accepted by the railway companies. I am pleased to have lived long enough to see continuous brakes universally adopted, for by them vast numbers of persons have been saved from injury or death.