186 REPORT— 1868. 
You have all read the accounts cf the vast experiments that haye lately been 
made in gunnery. I believe Dr. Fairbairn has been connected with those expe- 
riments on the shields designed for the purpose of resisting the heaviest modern 
artillery. I will not for a moment deny the value of these experiments; but I 
must say that, in my opinion, they would haye been more yaluable if they had 
been based on the well-Imown laws of the resistance of metals of the same 
quality to impact due to weight and velocity, I think that improyement in the 
structure of guns would haye been advanced with more certainty if the action 
of gunpowder upon the projectile had been clearly ascertained and defined. It 
is perfectly certain that gunpowder when exploded cannot act with less power 
than sixty tons upon the square inch; itis also certain that unless that power 
be immediately reduced we have no gun which it will not destroy; but the fact 
is that the moment the projectile moves, the enormous expansion of the pow- 
der is reduced with such rapidity that the metal has not time to yield and break 
before the pressure is removed and the danger is gone. This shows that the 
kind of metal you use, whatever its tenacity and hardness, should be capable 
of yielding to a certain extent, without absolutely breaking; but it is quite cer- 
tain that this sort of action is of such a nature that if it be continued to a cer- 
tain extent it must lead to the destruction of the gun, and that the question 
as to the life of a gun is only one of how many charges may be fired from it before 
it is absolutely destroyed. I say that the whole question of the mechanical action 
of the gunpowder gases should be absolutely determined and settled, and that it 
ought to be clearly understood by these who are engaged in designing guns, If 
they go on without this Inowledge they are merely proceeding at “ hap-hazard,” 
and are groping in the dark. 
The improvement of the communication between Hngland and the Continent is 
now daily exciting more and more attention. Admirably as the service is con- 
ducted, under existing circumstances, still the horrozs and delays of the middle 
passage, across the Straits of Dover, will, so long as they continue, restrict free 
intercourse with the Continent. Indeed, until a traveller can reach his destination, 
at Paris or Brussels, in the same carriage in which he started from London, this 
great desideratum cannot he said to have been attained. 
There are now two projects, more or less, before the public,—one for bridging the 
Channel, and the other for tunnelling beneath it. Before analyzing these projects 
I would make one general observation, viz. that any project involving an outlay 
(inclusive of interest during progress) of from forty to fifty millions sterling, and 
requiring from forty to fifty years for its execution, cannot with reason be enter- 
tained. 
With regard to the Bridge project, the latest proposition would appear to be to 
span the channel by a viaduct consisting of openings of three thousand feet each, 
The platform must of necessity be upwards of two hundred feet aboye the level of 
the sea. The piers would be ereéted on islets founded in a depth of water of thirty 
fathoms, Now, bearing in mind that to bridge the Thames in the most economical 
manner inyolves a cost of about £125 per lineal foot, and applying this as a stand- 
ard, contrasting the facilities in the one case with the obvious enormous difficulties 
and contingencies in the other, the relative cost of the latter must greatly exceed 
four times that of the former; the minimum cost, therefore, of the channel viaduct 
cannot be taken at less than £500 per lineal foot, which at once brings the cost up 
to fifty millions sterling, without taking into account current interest. With these 
remarks we may dismiss the Bridge question. 
A recent article in the ‘Times’ describes the Tunnel project: the main tunnel 
is to be constructed at such a depth below the bottom of the channel as, it is hoped, 
would enable a stratum to be reached which would be impervious to infiltration, 
Nevertheless there is some uncertainty on this point. It is proposed to commence 
by driving a trial heading at a cost of two millions sterling. The estimated cost 
of the main tunnel was stated at, I believe, eight millions, raising the total esti- 
mated cost to ten millions, Without going into all the details of construction, I 
will only allude to the two main features—the driving of the heading, and the 
completion of the main tunnel. 
It is obvious that the heading can only be driyen from the two ends; and as- 
