During the progress of the survey, a register of the rise and fall of the tides was regularly kept at Hynish on the neighbouring Island of Tyree; and from those observations it was determined, that the rise at that place is between twelve and thirteen feet at high spring tides, and three feet at dead low neap tides; and observations subsequently made while the works were in progress, gave the same results at the Rock of Skerryvore. It is high water at the Rock at full and change of the moon, at five hours and twenty-five minutes. The tides round the Skerryvore are not remarkable for their rapidity. In spring-tides the velocity is between four and five miles, and in neap-tides between two and three miles an hour. The flood sets to the N.N.E., and the ebb to the S.S.W. CHAPTER II. PRELIMINARY ARRANGEMENTS AND WORKS, INCLUDING SURVEY OF THE ROCKS, AND OPENING OF QUARRIES, FROM 1834 to 1837. ~Survey of the Skerryvore Rocks.~ In this chapter I shall very briefly notice those preliminary arrangements which may be said to have been in a great measure preparatory to the commencement of the work itself. It has been already stated, that the erection of the Lighthouse was provided for in the Act of 1814; but so formidable did this work appear, that although it was repeatedly under consideration, it was not until the General Meeting of the Board, on the 8th July 1834, that any measures were taken to carry into effect the provisions of the Act. On that occasion it was moved by the late Mr MACONOCHIE, Sheriff of Orkney and Zetland, that the Engineer should be instructed to make the necessary survey, and to report as to the expense of erecting the Lighthouse. In terms of this remit, the survey of the Rocks was commenced in the autumn of 1834; but from the broken state of the weather, little was effected at that time beyond making the triangulation; and it was not until the summer of 1835 that the survey was completed from which the Chart, Plate No. II. was constructed. This survey was attended with much more labour than its extent would lead one to suppose, in consequence of its embracing the entire range of operations required in a more extensive nautical survey, and combining with the ordinary details required for a Chart, the minute accuracy in regard to surface and levels, which are always necessary for the purposes of the Engineer. * * * * *