WEAK POINTS OF THE ATMOSPHERIC BRAKE.
Although the atmospheric brake could, with light trains, make stops within the shortest distance it was desirable to stop trains with safety to the passengers and rolling stock, it possessed certain weak points which demanded remedy. In case of a train breaking in two,—an accident which frequently happens, especially on rough track,—there was danger of the engineer applying the brake without knowing that an interval existed between the cars, and allowing the rear end of the train to crash into the forward part. The signal given by the bell-rope breaking, had a tendency to lead to an accident of this character. Another objection to straight air was, that should derailment take place, or any accident happen that would rupture the pipes or their connections, the brake was rendered useless. These weak features did not interfere with the working of ordinary traffic; and as providing special appliances to meet cases of accident which are rare, does not generally receive much consideration, the brake might have been regarded as perfect enough for all practical purposes had it not failed to meet satisfactorily a condition of ordinary train service. As the length of trains was increased, it was found that the atmospheric brake was slow in action. When a long array of pipes and many cylinders had to be charged with air from the drum on the locomotive after the necessity for applying the brake became apparent, and before it would act, some seconds were required for the operation. Every additional car put upon the train increased the length of pipes and the cylinders to be filled, and so lengthened the time that elapsed between the instant danger was perceived and the time at which the brake began to perform its retarding work. The increase of time might be only a few seconds, but they would probably be priceless moments when an accident was impending.