The Sun.
London, England, 1851-01-31 00:00:00

SOCIETY OF ARTS.
THE BRITANNIA BRIDGE.

On Wednesday, the eighth ordinary meeting of this
society took place in John-street, fidelphi, when an
interesting paper was read by Mr. Grove, the secre-
tary, on the history and construction of the Britannia
Bridge. Mr. Grove stated that the bridge had derived
its name from a rock which divides that part of the
Menai river over which the structure is raised, and
which at low water exposes a surface about as large
as Trafalgar-square, but at high water is completely
covered. On this rock Mr. Stephenson proposed
originally to build a pier of masonry 130 feet long,
and 50 feet wide, from each side of which was to
spring an arch of 350 feet span, of cast iron, the height
of the underside of the crown being 103 feet above
high-water mark.
On this design being made public it met with a
great deal of opposition from those interested in the
navigation of the straits, who urged that the difficul-
ties arising from the rapid tides, the uncertain eddies,
and the sunken rocks, would be greatly aggravated
by the erection of a large pier on the Britannia Rock.
Mr. Stephenson was therefore unable to carry out his
original project; and he found there was no resource
left him but in some way to contrive a straight beam
or girder ; and, on thinking over the possibility of a
" trellis bridge" the idea of a tube of wrought iron
entered his mind. Having well considered his subject,
with reference to the particular form the tube should
assume, and also in regard to the properties of
wrought iron, as distinguished from those of cast iron,
Mr. Stephenson obtained permission to make a series
of experiments for the purpose of gaining the know-
ledge he required. The result was that the rectan-
gular form of tube was selected as being stronger
than the oval and cylindrical tube. This point being
decided, the next question was as to the means to be
adopted in fixing the different parts together, and the
method chosen was that of using red hot rivets instead
of welding the iron, as in smaller operations. Mr.
Grove then proceeded to detail the various processes
adopted in carrying out the undertaking, and
described the mechanical difficulties which had to be
overcome by the engineers before the work could be
completed. In proof of the success which had at-
tended Mr. Stevenson's exertions in this matter, Mr.
Grove stated that the same method of construction*

was being adopted in railway bridges, which, though
soutti In proportion to the Britannia Bridge, were
far beyond the greatest limits to which the same
process had ever been carried previous to the
formation of this gigantic structure. After relating
the history of the bridge—from its projection
to the mechanical difficulties which surrounded its
progress to completion, Mr. Grove related a few
interesting statistics with a view to point out
the extraordinary proportions of the structure. The
total weight of the tubes was nearly 11,000 tons,
being greater than that of four 120 gun ships with all
their crews and stores on board. This weight was
made up of 9,360 tons of wrought iron, and more than
1,200 tons of cast iron and timber. These were com-
posed of about 186 separate pieces of iron, pierced by
more than seven millions of holes, and united by up-
wards of two millions of rivets of the angle and T
iron, embracing a space of not less than 83 miles.
The weight of the lifting chains alone at each end of
the tube was more than 40 tons, which, with " the
crosshead and rain of the press," made a total of
more than sixty tons to be lifted More any
effect could be produced on the tube itself. Of the
masonry in the towers and abutments, there were
about 1 millions of cubic feet, which would form a
pyramid whose base would equal the area of
Leicester-square, and whose height was 80 feet, and
the weight in all 105,000 tons Allowing 12 working
hours in the day and six days to the week, this
masonry was prepared and laid at the rate of 3 cubic
feet per minute during the whole time of its con
struction. Having related these particulars, Mr. Grove
concluded by saying that he was employed upon the
great undertaking during the most interesting period
of its operation, and that he availed himself of the
opportunity thus afforded of making himself ac-
quainted with all the details of the construction. The
" paper" was most interesting and instructive through-
out, and the reader was assisted in his descriptions by
models and diagrams, lent to him for the occasion by
Mr. Robert Stephenson, the directors of the Chester
and Holyhead Railway, Professor Cowper, and others,