1188 REPORT— 18809. 
side entrances, earthenware socket pipes with cement joints, and other interesting 
details connected with 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 Institution of Civil Engineers, that the bridge across the Dee at 
Chester was the ‘largest stone arch om record.” That is not so. The Dee bridge- 
consists of a single segmental arch 200 ft. span and 42 ft. rise; but across the 
Adda, in Northern Italy, was built, in the year 1577—more than 500 years 
a similar segmental arch bridge of no less than 257 ft. span and 68 ft. rise, ae 
rario not long since published an account of this, for the period, colossal work, 
from which it would appear that its lite was but 39 years, the bridge having been 
destroyed for military reasons on December 21, 1416. I believe our American — 
cousins claim to have built the biggest existing stone arch bridge in the world, that 
across the Cabin Johns Creek, but the span, after all, is only 215 ft., or ten per cent. 
smaller than the 500-year-old bridge. n timber bridges, doubtless, the Americans. 
will ever head the list, for the bridge of 340 ft. span built across the Schuylkill 
three-quarters of a century ago will probably 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 lightened 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. Armstrong. Addressing you in 1854, Sir William Arm- 
strong explained 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, in-- 
termittent 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 indis-- 
pensable, would appear to be limitless. I should be sorry indeed to have anything 
to do with building the Forth bridge if hydraulic po Bere were not at hand to. 
do a giant’s work. Let me shortly deseribe 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 rey = 
sheaves, the whole arm being raised with the load by a 4-in. direct-acting ram of” 
6 ft. stroke. A total length of no less than 60 mules of steel plates, ing in 
thickness from 1? in. to $ in., have to be bent to radii of from 6 ft. to 9 in., which® 
is done in heavy cast-iron dies squeezed together by four rams of 24 in. in diameter, . 
and the same stroke. With the ordinary working pressure of 1,000 Ibs. per square 
inch, the power of the press is thus about 1,750 tons. Some 3,000 pieces, shaped 
like the lid of a box, 15 in. by 12 in. wide, with a 3-in. deep rim all round, were 
required to be made of }-in. steel plate, and this was easily effected in two heats- 
by a couple of strokes of a 14-in. ram. In numberless other instances steady 
hydraulic pressure has been substituted by Mr. Arrol, cur able contractor, for the- 
usnal eutting and welding under the blacksmith’s hammer. 
Hydraulic appli are also an indispensable part of the scheme for erecting” 
the great 1,700 ft. 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 plat- 
forms weighing in some instances more than 1,000 tons. It is hardly necessary to 
say that every rivet in the bridge will be closed up by hydraulic power, 
machines being in many instances of novel design, ially adapted to the work. 
Thus the bed-plates, which in ordinary bridges are simple castings, in the 
