RAILWAY SIGNALS.

Globe, Volume II, Issue 201, 30 January 1875, Page 4

RAILWAY SIGNALS.

At a meeting of the British Association, held at Belfast in August last, Professor L Thomson, C.E., Glasgow University, read a paper on the above subject After referring at some length to the number of railway accidents and their causes, he went on to say—- “ There can be no doubt, however, but that of the accidents which do occur many arise from causes of kinds more or less preventible according to the greater or less degree in which due precautions may be adopted. Gradually, during a period of twenty or thirty years past, a very fine system of watching, signalling, and otherwise arranging for the safety of trains has been contrived and very generally introduced along our principal lines of railway. In saying this, 1 allude chiefly to the block system of working railways, with the aid of telegraphic signals, and interlocking mechanisms for the working of the points and signals. The latest important step in the development and application of the block system is one which has just now been made in Scotland on the Caledonian Railway. Before explaining its principles, I have first to mention that a semaphore arm raised to the horizontal position is the established danger signal, or signal for debarring an engine driver from going past the place where the signal is given. Now, the ordinary practice has been, and still is, to keep the semaph re arm down from that level position, and so to leave the line open for trains to pass, except when the line is blocked by a train or other source of danger on the block section in front of that semaphore, and only to raise the semaphore arm exceptionally as a signal of danger in front. The new change, or improvement, now made on the Caledonian Railway consists mainly in arranging that along a line of railway the semaphore arms are to be regularly and ordinarily kept up in the horizontal position for prohibiting the passage of any train, and that each is ouly to be put down when an approaching train is, by an electric signal from the cabin behind. announced to the man in charge of that semaphore as having entered on the block section behind, and when further, that man has, by an electric signal sent forward to the next cabin in advance, inquired whether the section in advance of bis own cabin is clear, and has received in return an electric signal meaning, “The line clear; you may put down your debarring signal, and let the train pass your cabin.” The main effect of this is that along a line 01 railway the signals are to be regularly and ordinarily standing up in the debarring position against allowing any train to pass; but thst just aseacb train approaches, and usually before it has come in sight, they go down almost as if by magic, and so open the way in front of the train, if the line is ascertained to be duly safe in front ; and that immediately on the passage of the train they go up again, and by remaining up keep the road closed any engine or train whose approach has not been duly announced in advance, so as to be known at the first and second cabins in front of lb, and kept closed, unless the entire block section between those two cabins is known to have been left clear by the last preceding engine or train having quitted it, and is sufficiently presumed uot to have met with any other obstruction, by shunting of carriages or waggons, or by accident, or in any other way. This new arrangement, which appears to be a very important improvement, has already been brought into action with success on several sections of the Caledonian Railway ; and it is being extended as rapidly as possible on the lines of that railway where the oidinary mode of working the block system has hitherto been adopted. The mech -nisms and arrange meuts I have now briefly mentioned are ouly a portion of the numeious contiivances in use for abatement of clanger in railway traffic. It is to he understood that by no mechanisms whatever can perfect immunity from accidents be expected. The mechanisms axe liable to break or to go wrong. They

must be worked by men, and the men are liable to make mistakes or failures. We shall continue to have accidents ; but, if we cannot do away with every danger, that is no leason why we should not abate as many dangers as we can.