The theoretical objection to the automatic brake is obvious. In case of any derangement of its machinery it applies itself, and, should these derangements be of frequent occurrence, the consequent stoppage of trains would prove a great annoyance, if not a source of serious danger. This objection is not sustained by practical experience. The triple valve, so called, is the only complicated portion of the automatic brake, and this valve is well protected and not liable to get out of order.[24] Should it become deranged it will stop the working of the brake on that car alone to which it belongs; and it will become deranged so as to set the brake only from causes which would render the non-automatic brake inoperative. When anything of this sort occurs, it stops the train until the defect is remedied. The returns made to the English Board of Trade enable us to know just how frequently in actual and regular service these stoppages occur, and what they amount to. Take, for instance, the North Eastern and the Caledonian railways. Both use the automatic brake. During the last six months of 1878 the first ran 138,000 train miles with it, in the course of which there were eight delays or stoppages of some three to five minutes each occasioned by the action of the triple-valve; being in round numbers one occasion of delay in 17,000 miles of train movement. On the Caledonian railway, during the same period, four brake failures, due to the action of the triple-valve, were reported in runs aggregating over 62,000 miles, being about one failure to 15,000 miles. These failures moreover occasioned delays of only a few minutes each, and, where the cause of the difficulty was not so immediately apparent that it could at once be remedied, the brake-tubes of the vehicle on which the difficulty occurred were disconnected, and the trains went on.[25] One of these stoppages, however, resulted in a serious accident. As a train on the Caledonian road was approaching the Wemyss Bay junction on December 14th, in a dense fog, the engine driver, seeing the signals at danger, undertook to apply his brake slightly, when it went full on, stopping the train between the distant and home signals, as they are called in the English block system. After the danger signal was lowered, but before the brake could be released, the signal-man allowed a following train to enter upon the same block section, and a collision followed in which some thirteen passengers were slightly injured. This accident, however, as the inspecting officer of the Board of Trade very properly found, was due not at all to the automatic brake, but to "carelessness on the part of the signal-man, who disregarded the rules for the working of the block telegraph instruments," and to the driver of the colliding train, who "disobeyed the company's running regulations." It gives an American, however, a realizing sense of one of the difficulties under which those crowded British lines are operated, to read that in this case the fog was "so thick that the tail-lamp was not visible from an approaching train for more than a few yards."