The sides, bottom, and top of these gigantic tubes are formed of oblong
wrought iron plates, varying in length, width, and thickness, according
to circumstances, but of amazing size and weight. They are so arranged
as to obtain the greatest possible strength, the whole being riveted
together in the strongest manner. In addition to the 1600 tons of
wrought iron in each of the four large pieces, an additional 200 tons
was used to form lifting frames, and cast iron beams for the purpose of
attaching the tube to those huge chains by which they were elevated. The
construction of the tubes is thus described in the London Illustrated
News, from which this account is derived:
"In order to carry out this vast work (the construction of the tubes),
eighty houses have been erected for the accommodation of the workmen,
which, being whitewashed, have a peculiarly neat and picturesque
appearance; among them are seen butcher's, grocer's, and tobacconist's
shops, supplying the wants of a numerous population. A day school,
Sunday school, and meeting-house also conspicuously figure. Workshops,
steam-engines, store-houses, offices, and other buildings meet the eye
at every turn; one is led to conclude that a considerable time has
elapsed since the works were commenced, yet it is little more than two
years ago. A stranger, on coming to the ground, is struck with wonder
when for the first time he obtains a near view of the vast piles of
masonry towering majestically above all the surrounding objects--strong
as the pillars of Hercules, and apparently as endurable--his eyes wander
instinctively to the ponderous tubes, those masterpieces of engineering
constructiveness and mathematical adjustment; he shrinks into himself as
he gazes, and is astonished when he thinks that the whole is the
developed idea of one man, and carried out, too, in the face of
difficulties which few would have dared to encounter."