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CHAPTER XIII. CRANES.
It appears that Mr. Stevenson was much perplexed as to what sort of cranes he should use in building the Bell Rock Lighthouse. His difficulties were twofold:—

First, In consequence of the dovetailed form of the stones he required a crane that would drop them as nearly as possible on the beds on which they were permanently to rest.

Second, Supposing he devised a guy crane that overcame this difficulty, what was to be done as the building rose in height, and the guys became too nearly perpendicular to admit of such a crane being used?

In his private notes Mr. Stevenson regrets that he could get no advice from anybody he consulted, all of whom recommended him to employ common sheer poles, such as had been used by Smeaton at the Eddystone; and he adds, “I may say, morning, noon, and night, these difficulties have haunted me.” But thrown back on his own resources, and appreciating the difficulty as no one else could so well do, he found, as is often the case, that he was his own best counsellor, and he succeeded in solving the problem that had given him so much concern, by inventing what he called the “moveable beam182 crane,” and also the “balance crane,” which are shown in Plate XI. The former, as modified to suit particular cases, is now in universal use for building purposes, and the latter has been employed in rearing most of our Rock Lighthouses, so that I think professional readers will not object to my giving Mr. Stevenson’s description of these cranes, as designed by him at the beginning of this century. He says:—

“In cranes of the common construction the beam is a fixture, and is placed at right angles to the upright shaft: but in the machine represented in the Plate (Fig. XI-1), its attachment is at the lower extremity of the crane, where it is moveable up and down upon a journal or bolt. This crane is therefore termed a moveable beam crane. The moveable property of the beam, in so far as the writer knows, is new, and possesses the advantage of laying any stone within its range perpendicularly on its site. This, from the dovetailed form of the stones at the Bell Rock, rendered it particularly fitted for this work, to which a crane of the ordinary construction could hardly be said to be applicable. At th............
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