If the gulf is wide, this operation might be carried on from both sides till the shears meet, and could be secured together in the middle, as in our illustration; and the roadway could then be constructed between them.
BRIDGE SHEARS.
Guano stages at Ichaboe
When vessels first went to the island of Ichaboe for guano, it was customary to require every new comer to bring two or three stout spars for the purpose of extending the landing jetty; and as each had the benefit of the spars left by former vessels, so each was expected to leave her own for the use of those who followed.
Owing to the irregularity of the rocky bottom, thickly covered with seaweed, the depth of water, and the distance from shore at which the surf began to break, all the ordinary methods of constructing a jetty were impracticable, especially when the object of each captain was to load his vessel as quickly and easily as possible, and to get away without expending the labour of his crew on works more than sufficient for his own service. Besides this, even had holes been bored, piles driven, and a staging laid down upon them, the platform, if permanently spiked down, would inevitably have been torn up by the surf in even a moderate gale; or, if loosely laid, would have been liable to such constant derangement as to be practically useless. It was necessary, therefore, that the base, while strong. enough to support the traffic, should present little or no surface for the waves to act upon, and that the roadway should be so elevated that breakers could not touch it. Even under these conditions, it was found that the first structures were washed away, and other forms had to be adopted; these could only be built on the north and east sides of the island; they were not less than 200ft. or 300ft. in length, and seldom or never in a straight line.
A heavy bower anchor, sometimes weighted by several lengths of chain frapped round it, was laid down well outside the surf, with one or two fifteen fathom lengths of chain, and to the end of this a stout hawser was bent on and carried to the shore, passing over and lashed to the intersection of a pair of stout poles set up as shears, and with its shore end leading to another anchor or secure fastening, to which, when the structure was completed, it could be tightly set up by means of tackles.
The first pair of shears having been erected, it was comparatively easy to erect others, and often as many as a dozen or sixteen pairs were fixed, the hawser passing over and serving as a ridge rope to them all. At about 12ft. above high water smaller spars were lashed fore and aft, so as to connect all the shear legs on either side through the whole length of the jetty, and others were laid across and well secured by cleats and lashings between each pair of legs, with some at shorter intervals, on which the roadway was constructed of planks and spars, sometimes nailed, but more generally securely lashed. At the end of this staging was a small platform, slung by tackles to the outermost pair of shears, and capable of being raised or lowered, so that boats might lie alongside it either at high or low water.
GUANO STAGE AND FLYING RAILWAY AT ICHABOE.