QUESTION 535. _If the lifting shaft itself or its vertical arm, the reverse lever or rod, should break, what can be done?_ _Answer._ If it is impossible to devise any temporary substitute or method of mending them, both links can be blocked up as described above. QUESTION 536. _In case the throttle-valve should fail, what should be done?_ _Answer._ If such an accident occurs, especially if it happens about a station, it is attended with great danger. If it is found that steam can not be shut off from the cylinders with the throttle-valve, then the reverse lever should be placed in the middle of the sector. If this does not prevent the engine from moving, the reverse lever should be alternately thrown into forward and then into back gear, and at the same time every aperture, such as the safety-valve and heater cocks, should be opened, and every means be taken to cool the boiler as quickly as possible. The fireman should open the furnace door, close the ash-pan dampers, and start the blower so as to draw a strong current of cold air into the furnace and through the tubes. At the same time the injector should be started and the fire drawn as quickly as possible. After the boiler is cooled, the cover of the steam-dome may be removed and the valve examined if the defect can not be discovered in any other way. Of course if the accident occurs on the open road, the train must be at once protected by sending out signals in each direction. QUESTION 537. _What must be done in case a coupling breaks?_ _Answer._ When a coupling between the cars or tender breaks, if the front end of the train is immediately stopped, there will be danger that the back end of it, which is broken loose, will run into the front end, and thus do great damage. As it always occurs, when a coupling of a passenger train breaks, that the signal bell in the cab is rung, the first impulse of a runner under such circumstances is to stop the engine. He should, however, be careful not to do so if on shutting off steam he finds that the train has broken in two, but should at once open the throttle in order to get the front end of the train out of the way of the rear end. The ease with which the speed of a train is arrested with continuous brakes has increased the danger of accident from this cause. Usually a runner learns by the sudden start of the engine that the train has separated, and when that occurs he should never apply the brakes. QUESTION 538. _If from any cause the supply of water in the tender becomes exhausted, what must be done?_ _Answer._ It is best, if it can be done without risk of injury to the engine, to run the train on a side track and then draw the fire. If no water can be obtained near enough to supply the tender with buckets, help must be sent for; but if there is a well, stream or pond of water near, the tender can be partly filled by carrying water.