1874.] Engineering. 413 
dynamometer, showed that, making allowance for the slip of the screw, which 
is a legitimate expenditure of power, only about 45 per cent of the power 
exerted by the steam is usefully employed in propelling the ship, and that no 
less than 55 per cent is wasted in friction of engines and screw, and in the 
detrimental reaction of the propeller on the stream-lines of the water closing 
in around the stern of the vessel. 
Railways.—The numerous railway accidents which have taken place of late 
have necessarily direGted the attention of engineers and others interested in 
the working of railways to the question as to how accidents may be avoided, 
or, at least, lessened. This subje& has been taken up by Captain Tyler, who 
recently read a paper before the Society of Arts on the ** Working of Railways,” 
and on simplicity as the essential element of safety and efficiency in the 
working of railways. From this paper we learn that the various classes of 
collision, and the accidents at facing-points, may together be roughly stated 
to comprise from two-thirds to three-fourths of the more serious casualties to 
railway trains. Railway working, which was at first easily condudted, is 
becoming a science with its separate branches, and deserves, therefore, care- 
ful study and investigation. Questions as to the arrangement ard working of 
points and signals, and as to preserving intervals of time and space between 
trains and their accessories, enter more or less into the causes of the majority 
of railway accidents. 
With regard to signals, by the application of locking and other apparatus 
it is possible to prevent nearly all those accidents which occur in consequence 
of any mistake of the signalman. Confli@ between signals, and confli@ 
between points and signals, may alike be avoided, and a good combination of 
locking, bar and bolt, may be made to ensure that the facing-points are com- 
pletely over before the proper signal is lowered, and may also prevent them 
from being moved during the passage ofa train. As regards signalmen, the 
selection and regular training of fit men for the performance of such duties as 
they have to perform; the employment of responsible inspectors for constant 
supervision, and the preservation of rigid discipline; the command of a 
sufficient number of relieving men to take Sunday duty and to replace signal- 
men absent from sickness or otherwise, and the maintenance in high condition 
of the whole of the apparatus, are matters of obvious importance; but 
experience has shown that it is by no means unnecessary to refer to them. 
By attention to these considerations, the dangers of facing-points are for the 
most part obviated, and engines and trains may be turned in and out, and 
across one another, with marvellous rapidity and facility, and in a way that 
would be otherwise impossible. 
The next branch of the subje& is that which refers to the preservation of 
intervals between trains; and this is best done by what is known as the block 
system. There are many descriptions of instruments for working the block 
system, and various rules and regulations applicable to it on different lines of 
railway. The main principle involved is, simply, by the division of a line into 
block sections, and by allowing no engine or train to enter a block section until 
the previous engine has quitted it, to preserve an absolute interval of space 
between engines and trains. 
To sum up the whole case, it is necessary, in railway working, to deal with 
men and mechanism. Men are fallible, and mechanism may fail. The com- 
plications of railway construction and traffic have increased enormously, and 
are still increasing. At some points, the lines, the sidings, and the crossings 
are so numerous, and the traffic is so constant, that the employment of the 
best means and appliances is unavoidable. In other localities, of severe 
gradients or obstructed view, or when greater danger is otherwise incurred, 
similar means and appliances are also indispensable. These points and 
localities become more and more numerous, and ample experience has now 
been obtained as to the most efficient modes of working. The result of that 
experience has plainly demonstrated that mistakes and accidents may best be 
avoided, and efficiency of working may best be attained—(1) By judicious 
VOL. IV. (N.S.) eG 
