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Sept. 17, 1885 | 
that a year’s experience showed the saving in horseflesh to be 
fully 33 per cent. 
Although these views seem childlike enough from our present 
standpoint, I have no doubt that as able and enterprising 
engineers existed prior to the age of steam and steel as exist 
now, and their work was 
different in direction. In the important matter of water supply 
to towns, indeed, I doubt whether, having reference to facility 
of execution, even greater works were not done 2000 years ago 
than now. Herodotus speaks of a tunnel 8 feet square, and 
nearly a mile long, driven through a mountain in order to 
supply the city of Samos with water; and his statement, though 
long doubted, was verified in 1882 through the abbot of a 
neighbouring cloister accidentally unearthing some stone slabs. 
The German Archzological Society sent ont Ernst Fabricius to 
make a complete survey of the work, and the record reads like 
that of a modern engineering undertaking. Thus, from a 
covered reservoir in the hills proceeded an arched conduit about 
tooo yards long, partly driven as a tunnel and partly executed 
on the ‘‘ cut and cover ” system adopted on the London under- 
ground railway. The tunnel proper, more than 1100 yards in 
length, was hewn by hammer and chisel through the solid lime- 
stone rock. It was driven from the two ends like the great 
Alpine tunnels, wishout intermediate shafts, and the engineers 
of 2400 years ago might well be congratulated for getting only 
some dozen feet out of level and little more out of line. From 
the lower end of the tunnel branches were constructed to supply 
the city mains and fountains, and the explorers found ventilating 
shafts and side entrances, earthenware socket-pipes with cement 
joints, and other interesting details connected wifh the water- 
supply of towns. 
In the matter of masonry bridges, also, as great works were 
undertaken some centuries ago as in recent times. Sir John 
' Rennie stated, in his presidential address at the Institute of 
Civil Engineers, that the bridge across the Dee at Chester was 
the ‘‘ largest stone arch on record.” That is not so. The Dee 
Bridge consists of a single segmental arch 200 feet span and 
42 feet rise ; but across the Adda, in Northern Italy, was built, 
in the year 1377—more than 500 years ago—a similar segmental 
arch bridge of no less than 237 feet span and 68 feet rise. 
Ferario not long since published an account of this, for the 
period, colossal work, from which it would appear that its life 
was but thirty-nine years, the bridge having been destroyed for 
military reasons on December 21, 1416. I believe our American 
cousins claim to haye built the biggest existing stone arch bridge 
in the world—that across the Cabin Johns Creek ; but the span, 
after all, is only 215 feet, or 10 per cent. smaller than the 500- 
year-old bridge. In timber bridges, doubtless, the Americans 
will ever head the list, for the bridge of 340 feet span built 
across the Schuylkill three-quarters of a century ago will pro- 
bably never be surpassed. Our ancestors were splendid workers 
in stone and timber, and, if they had been in possession of an 
unlimited supply of iron and steel I fear there would have been 
little left for modern bridge-builders to originate. 
The labours of the present generation of engineers are light- 
ened beyond all estimate by labour-saving appliances. To prove 
how much the world is indebted to students of this branch of ! 
mechanical science, and how rapid is the development of a really 
good mechanical notion, it is only necessary to refer to the 
numerous hydraulic appliances of the kind first introduced forty 
years ago by a distinguished past-President, Sir W. G. Arm- 
strong. Addressing you in 1854, Sir William Armstrong ex- 
plained that the object he had in view from the first was ‘‘to 
provide, in substitution of manual labour, a method of working 
a multiplicity of machines, intermittent in their action and 
extending over a large area, by means of transmitted power, 
produced by a steam-engine and accumulated at one central 
point.” The number of cases in which this method of working 
is a desideratum, or even indispensable, would appear to be 
limitless. I should be sorry, indeed, to have anything to do 
with building the Forth Bridge if hydraulic appliances were not 
at hand to do a giant’s work. Let me shortly describe to you 
what we are doing there at the present time. More than 42,000 
tons of steel plates and bars have to be bent, planed, drilled, 
and riveted together before or after erection, and hydraulic 
appliances are used throughout. The plates are handled in the 
shops by numerous little hydraulic cranes of special design, 
without any complication of multiplying sheaves, the whole arm 
being raised with the load by a 4-inch direct-acting ram of 6 feet 
stroke. A total length of no less than 60 miles of steel plates, 
as beneficial to mankind, though | 
NATORE 
491 
ranging in thickness from 14 inches to 2 inch, have to be bent to 
radii of from 6 feet to 9 inches, which is done in heavy cast-iron 
dies squeezed together by four rams of 24 inches in diameter, 
and the same stroke. With the ordinary working pressure of 
1000 lbs. per square inch, the power of the press is thus about 
1750 tons. Some 3000 pieces, shaped like the lid of a box, 
15 inches by 12 inches wide, with a 3-inch deep rim all round, 
were required to be made of 4-inch steel plate, and this was 
easily effected in two heats by a couple of strokes of a 14-inch 
ram. In numberless other instances steady hydraulic pressure 
has been substituted by Mr. Arrol, our able contractor, for the 
usual cutting and welding under the blacksmith’s hammer. 
Hydraulic appliances are also an indispensable part of the 
scheme for erecting the great 1700 feet spans. Massive girders 
will be put together at a low level, and be hoisted as high as the 
top of St. Paul’s Cathedral by hydraulic power. Continuous 
girders, nearly a third of a mile in length, will be similarly 
raised. Not only the girders, but workmen, their sheds, cranes, 
and appliances will be carried up steadily and imperceptibly as 
the work of erection proceeds, on platforms weighing in some 
instances more than 1000 tons. It is hardly necessary to say 
that every rivet in the bridge will be closed up by hydraulic 
power, the machines being in many instances of novel design, 
specially adapted to the work. Thus the bed-plates, which in 
ordinary bridges are simple castings, in the Forth Bridge are 
necessarily built up of numerous steel plates, the size of each 
bed-plate being 37 feet long by 17 feet 6 inches wide. To grip 
together the 47 separate plates into a solid mass, 3800 rivets 
1{ inches in diameter with countersunk heads on both sides are 
required, and, remembering that the least dimension of the bed- 
plate is 17 feet 6 inches, it will be seen that the ordinary ‘‘ gap”’- 
riveter would not be applicable. A special machine was there- 
fore designed by Mr. Arrol, consisting of a pair of girders and 
a pair of rams, between which the bed-plate to be riveted to- 
gether lies. A double ram machine had for like reasons to be 
devised for riveting up the great tubular struts of the bridge. 
Not merely in the superstructure, but in the construction of 
the foundations, were hydraulic appliances of a novel character 
indispensable at the Forth Bridge. Huge wrought-iron caissons 
or cylinders, 70 feet diameter and 72 feet high, were taken up 
and set down as readily asa man would handle a bucket. In 
sinking these caissons through the mud and clay of the Forth 
compressed air was used. When the boulder-clay was reached 
the labour of excavating the extremely hard and tenacious mate- 
rial in the compressed-air chamber proved too exhausting, pick- 
axes were of little avail, and the Italian labourers who were 
chiefly employed lost heart over the job altogether. But a giant 
power was at hand, and only required tools fit for the work. 
Spades with hydraulic rams in the hollow handles were made, 
and, with the roof of the compressed air-chamber to thrust 
against, the workmen had merely to hold the handle vertically, 
turn a little tap, and down went the spade with a force of three 
tons into the hitherto impracticable clay as sweetly as a knife 
into butter. Probably, when addressing you thirty years ago, 
Sir William Armstrong never anticipated that a number of 
hydraulic spades would be digging away in an electrically lighted 
chamber or diving-bell, 70 feet diameter and 7 feet high, 90 
feet below the waves of the sea; but still the spades come 
strictly within the definition of the class of machines, inter- 
mittent in their action and extending over a large area, which 
it was his aim tointroduce. It would be possible, indeed, with 
the appliances at the Forth Bridge, to arrange that the simple 
opening of a valve should start digging at the bottom of the sea, 
riveting at a height of nearly 400 feet above the sea, and all 
the multifarious operations of bending, forging, and hoisting, 
extending over a site a mile and a half in length. 
It would not only be impossible to build a Forth Bridge, but 
it would be equally impossible to fight a modern ironclad with- 
out the aid of hydraulic appliances. Most of the Presidents of 
this Section have referred in the course of their addresses to our 
navy, and certainly the subject is a tempting one, for the pro- 
gress of mechanical science in recent years could not be better 
illustrated than by a description of the innumerable appliances 
which go to the making and working of a modern ironclad. 
Let me quote a single passage from a pamphlet by a naval 
officer, which caused a great stir a few years before the Crimean 
war, that I may recall to your minds what was the speed and 
what the armament of our fleet at that comparatively recent 
period. ‘‘Conceive,” said Capt. Plunkett, R.N., ‘‘a British 
and French fleet issuing simultaneously from Spithead and 
