The precision and accuracy of the signal-machinery employed at important stations and junctions have of late years been much improved by an ingenious contrivance, by means of which the setting of the signal prepares the road for the coming train. When the signal is set at "Danger," the points are at the same time worked, and the road is "locked" against it; and when at "Safety," the road is open--the signal and the points exactly corresponding. The Electric Telegraph has also been found a valuable auxiliary in insuring the safe working of large railway traffics. Though the locomotive may run at sixty miles an hour, electricity, when at its fastest, travels at the rate of 288,000 miles a second, and is therefore always able to herald the coming train. The electric telegraph may, indeed, be regarded as the nervous system of the railway. By its means the whole line is kept throbbing with intelligence. The method of working electric signals varies on different lines; but the usual practice is to divide a line into so many lengths, each protected by its signal-stations, the fundamental law of telegraph working being that two engines are not to be allowed to run on the same line between two signal-stations at the same time. When a train passes one of such stations, it is immediately signaled on--usually by electric signal-bells--to the station in advance, and that interval of railway is "blocked" until the signal has been received from the station in advance that the train has passed it. Thus _an interval of space_ is always secured between trains following each other, which are thereby alike protected before and behind. And thus, when a train starts on a journey of it may be hundreds of miles, it is signaled on from station to station, and "lives along the line," until at length it reaches its destination, and the last signal of "train in" is given. By this means an immense number of trains can be worked with regularity and safety. On the Southeastern Railway, where the system has been brought to a state of high efficiency, it is no unusual thing during Easter week to send 570,000 passengers through the London Bridge Station alone; and on some days as many as 1200 trains a day.