V.—Suggestions for an Apparatus for Registering the Tides.—By Lieutenant J. Campbell.
TO THE EDITOR OF THE MADRAS JOURNAL,
Dear Sir,—Mr. Prinsep in his letter to you regarding the observation of the height and time of arrival of the tide wave, having offered no suggestion as to how the observation may be made, I therefore offer the following remarks. On the east coast of the Peninsula the surf every where prevents any possibility of ever guessing the time and heights of high water, and in the small rivers the bar is always so shallow as to prevent the influx of sufficient water, so that the head of the river is always much below the surface of the sea, and the current continues to run in long after the time of high water, until the sea has again fallen to the level of the river.
I believe an attempt was made sometime ago to register the tide by a float in the end of an iron pipe brought in from beyond the surf, but I believe it soon choaked with sand. I conceive that the required observations may be made beyond the surf, by having a large bamboo with the divisions bored through, set up beyond the surf and supported by four ropes underwater, attached to small wooden anchors, the lower end may be allowed to enter six feet into the sand, and a round board fastened to the bamboo will prevent its sinking further. Above this board an aperture should be cut to allow the water to enter and the sand to fall out, which may be thrown in at top. The top of the bamboo being five feet higher than high water mark, the height of the water within the bamboo may be shewn by a rod attached to a cork float, and a flat wooden scale may be fixed on the rod with inches painted on it, which can be read off by a telescope from the shore. A piece of wire passing through a slit in the scale will ensure its being kept parallel to the shore.
A palmira tree might be used for the bamboo, the tree being split into two pieces and the pith removed, the pieces being again fastened together with rope.
John Campbell,
Assistant Surveyor General.
23d August 1837.
