or fy 
34 W. H. WARREN. 
important part of this undertaking is a tunnel, which is thirty- 
two chains long. The permanent way consists of eighty pound 
T rails, laid as already described. 
The safe working of a railway intimately concerns all travellers, 
and few probably have observed the extent of the safety appliances 
at present in use on our lines, or the vast improvements that have 
been made in this direction during the last few years. To the 
uninitiated passenger the sounding of the engine whistle, the 
movement of a signal, or the varying coloured lights exhibited by 
night, seem to embrace all that apparently is necessary to enable 
the train, with its living freight, to travel over the rails in safety. 
The interlocking of points and signals, which provides for the 
economical and safe working of station yards, junctions, and 
sidings, has been largely extended, at the present time being in 
use at about three hundred places, or fifty-five per cent. of the 
total number. By this system the points and signals at stations 
and junctions are manipulated either from an elevated signal-box, 
lever frame fixed on platform, or ground levers, controlled by 
keys or rod locking from the main apparatus, which places the 
whole of the points and signals under the control of one man, 
giving almost absolute safety. The points of outlying sidings 
are secured by what is known as the Annett’s lock, the key of 
which is attached either to the “ staff” or “tablet,” so that it is 
impossible for a second train to be on that part of the line while 
the siding is being used, and ensures that the points must be 
properly set and locked before the staff or tablet key can be re- 
moved for the train to continue on its journey. 
Most travellers are familiar with the rows of rods and wires, 
with their innumerable cranks, wheels, and rollers by which the 
gear is actuated; but the arrangement known as the “absolute 
block system” is to most persons an absolute mystery. Briefly, 
the block system means the dividing of a line of railway into 
sections, all of which are in electrical communication with one 
another, the object of which is to prevent more than one train at 
