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. [Sidenote: Leading Lights suggested.] A Beacon of any form, unprovided with a light, must always be considered an imperfect land-mark, and therefore various modes have been contemplated, for more completely pointing out the position of the Carr Rock. It has been proposed that phosphoric lights should be exhibited from the top of the Building. This object, however, would be more certainly accomplished, by the erection of leading lights, upon the Island of May and Mainland of Fife. But these, with other plans which have been under the writer’s consideration, would necessarily be attended with a great additional expence, which, in the present instance, it is not thought advisable to incur. [Sidenote: Expence of the Carr Rock works.] Owing to the necessarily slow progress of the operations at the Carr Rock, the works were carried on partly in connection with the new Light-house on the Isle of May, and with the assistance of the ordinary shipping of the Light-house establishment. This renders it difficult to give a distinct estimate of the expence of the Beacon; but in so far as it can be collected, it may be stated, including all charges, at about L. 5000. _Stations on the Coast of Scotland, where Light-houses have been suggested as still necessary._