Page:Cassier's Magazine Volume XV.djvu/17

 structural work, and with all the difficulties attending the formation of an entirely new business with small means. Soon, however, the business began to grow, and then grew so rapidly that, in 1871, he was compelled to remove to roomier premises. Then was founded the business which is now carried on by Sir William Arrol & Co., Limited, at the Dalmarnock Iron Works, in the eastern outskirts of Glasgow. In these new and more extensive works Mr. Arrol was enabled to undertake larger contracts than previously in all kinds of structural work, railway bridges, etc. Here also boiler-making for a time was carried on to a considerable extent, but afterwards was set aside in favour of the particular class of work with which the name of Arrol is now associated. With the increasing size and importance of contracts, and consequently greater masses of material requiring to be handled, Mr. Arrol set about designing and making special drilling and riveting plant for the manipulation of material by the most improved and economical methods.

One of the most important contracts at this time was that with the Caledonian Railway Company for a bridge over the Clyde at Bothwell. This structure is a very high one, and Mr. Arrol adopted the novel method of building the bridge on land and rolling it out, span by span, and from pier to pier in front. Another contract was for the ironwork comprising the structural portion of the great Central Station at Carlisle. A larger one still was a contract for the Caledonian Railway Bridge over the Clyde, to carry this railway to the new Central Station. It was to be a large structure, in width sufficient to carry four pairs of rails, and high enough to allow the smaller class of vessels frequenting this portion of the Clyde to pass underneath. It was in connection with the drilling of the booms for the main girders of this bridge that he introduced the system of building these booms complete, passing a traveling drilling machine over them, with the drills in such positions as to make them capable of boring every hole in the entire boom. The depth of drilling in some instances was as much as seven inches of solid material. Not only was special drilling plant made to carry out this contract, but Mr. Arrol, perceiving the great advantage that would be obtained by a system of economical riveting (as the rivets were so large and so long that it was practically impossible to have satisfactory work performed by hand), set about designing plant for the purpose, and the outcome was the introduction of the hydraulic riveting machine, known under the title of Arrol's Patent, which has done so much to revolutionise riveting in the principal bridge-building and ship-building yards of Great Britain.

Important as were these operations, however, they were small compared with the next undertaking to which Mr. Arrol addressed himself, and which was destined to make his reputation and to bring him honour and fame. This was the construction of the great Forth Bridge. When Mr. Arrol first became associated with this great work, the design in hand was that of the late Sir Thomas Bouch, who was the engineer of the first Tay Bridge. Sir Thomas Bouch's plan for spanning the Forth was to throw a suspension bridge over the estuary on the same site as that on which the present bridge stands. This design provided for piers in practically the same positions as the present piers, with this difference, however, that the height of the suspension bridge erections would have been over 600 feet above high-water level. Sir Thomas Bouch's design would have produced a more graceful structure than the present one, but it would not have given the rigidity that is essential where heavy trains are continually passing over at high rates of speed. In the present structure the provision made for resisting wind pressure is much greater than in the original plan. It was, however, on the Bouch design that Mr. Arrol secured the contract for the bridge. He had already spent a large amount of money in preliminary operations, and in the erection of workshops, when suddenly the catastrophe of the fall of the Tay Bridge compelled a pause, and