[Sidenote: Application of the tide-machine described.]
The form and construction of the Carr Rock Beacon, both as originally intended, and ultimately executed, will be better understood by referring to Plate II., and to the annexed Description of the Plates. The motion to be given to the bell-apparatus, or tide-machine, was to be effected by admitting the sea water through a small aperture, of three inches in diameter, perforated in the solid masonry, communicating with a cylindrical chamber, in the centre of the building, measuring two feet in diameter, in which a float or metallic air-tank, was to rise and fall with the tide. The train of machinery for this apparatus was calculated for a perpendicular rise of only six feet, being equal to the lowest neap-tides on this coast. During the period of flood-tide, the air-vessel, in its elevation, by the pressure of the water, was to give motion to machinery for tolling the bell, and winding up a weight; which last, in its descent, during ebb-tide, was to continue the motion of the machine, until the flood-tide again returned to perform the joint operation of tolling the bell and raising the weight. A working model of a machine upon this principle having been constructed, it was kept in motion for a period equal to several months: this was effected by water run through a succession of tanks, raised by a pump from the lower one to the higher, thus producing the effect of flood and ebb tides. The time during which this apparatus was in action, having been ascertained by an index, a constant attendance upon the machine, during this protracted experiment, became unnecessary.
[Sidenote: General application of tide-machinery.]
The upper termination of the Beacon, in its present form, does not admit of the application of the tide-machine with the bell-apparatus. Experiments as applicable to this have, however, been tried with a wind-instrument, to be sounded by the pressure of the sea water; but it has not succeeded to the extent that seems necessary for a purpose of this kind. We have indeed thought, that the application of pressure as a power, communicated by the waters of the ocean, in mechanical operations, might be carried to almost any extent, by simply providing a chamber or dock, large enough for the reception of a float or vessel, of dimensions equivalent to the force required. This description of machinery is more particularly applicable in situations where the tides have a great rise, as in the Solway Firth , Bristol Channel, and other parts of the British seas; and at St Malo, on the coast of France.
