TRANSACTIONS OF THE SECTIONS. 4) N39 
tained to be duly safe in front; and that immediately on the passage of the train 
they go upagain, and, by remaining up, keep the road closed against 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 it and kept closed, unless the entire block 
section between those two cabins is known to have been left clear by the last pre- 
ceding engine or train having quitted it, and is sufficiently presumed not 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 suecess on several sections of the Caledonian 
Railway ; and it is being extended as rapidly as possible.on the lines of the Cale- 
donian Company, where the ordinary mode of working the block system has hitherto 
been adopted. 
The mechanisms and arrangements I have now briefly mentioned are only a por- 
tion of the numerous contrivances in use for abatement of danger in railway-trafiic. 
Itis to be understood that by no mechanisms whatever can perfect immunity from 
accidents be expected. The mechanisms are 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 reason why we should not abate as many dangers as we can. 
Within the past twenty years very remarkable progress has been made in steam- 
navigation generally, and more especially, I would say, in oceanic steam-navigation. 
In this we meet with the realization of great practical results from the combination 
of improved mechanical appliances and of physical processes depending on a more 
advanced knowledge of thermodynamic science. 
The progress in oceanic steam-navigation is due mainly to the introduction jointly 
of the screw propeller, the compound engine, steam-jacketing of the cylinders, super- 
heated steam, and the surface-condenser. 
The screw propeller, in its original struggle for existence, when it came into 
competition with its more fully developed rival, the paddle-wheel, met with favour- 
ing circumstances in the want then strongly felt of means suitable for giving a 
smal] auxiliary steam-power to ships arranged for being chiefly propelled by sails. 
For the accomplishment of this end the paddle-wheel was ill suited ; and so the 
screw propeller got a good beginning for use on long oceanic voyages. Afterwards, 
in the course of years, there followed a long series of new inventions and improved 
designs in the adaptation of the steam-engine for working advantageously with the 
new propeller ; and it has resulted that now, instead of the screw being used as an 
auxiliary to the sails, the sails are more commonly provided as auxiliaries to the 
screw. For long oceanic voyages it became very important or essential to get 
better economy in the consumption of fuel. In order to economize fuel, high-pres- 
* [Since the delivery of this address, a remark by the editor of ‘Engineering,’ in the 
issue of that Journal for August 28, 1874, has come under my notice, in which he denies 
the supposed novelty of the system of signalling here described as newly introduced on 
the Caledonian Railway. He states that the system described has been in use for many 
years past on several railways, and that, amongst others, the Metropolitan Railway has 
never been worked upon any other system. Also he says that on a portion of the Great 
Eastern (then the Eastern Counties Railway) the system was in use upwards of twenty 
years ago. On the other hand, I learn from officers of the Caledonian Railway engaged 
in carrying out the alteration of system on the lines of the Caledonian Company, that 
they think the system as introduced on their railway has still much of novelty in com- 
parison with any thing previously done on any line extending over long distances in the 
country, and that though the Metropolitan Railway be worked on a system similar in 
some respects to that which they are introducing, yet the whole circumstances of that 
urban railway are so different from those of railways extending through the country, as 
to leave the introduction of the system here described on an ordinary railway, such es 
the Caledonian, still to be regarded as a change presenting important features of novelty 
in a practical point of view. 
Having now mentioned these statements, I prefer to leave any further discussion of 
the distinctions of different systems which have been or are in use, and of exact points of 
novelty in their introduction, to those who may be in possession of fuller evidence on the 
subject than what has hitherto been obtained by me.—JamEs Tomson, November 1874.] 
