What has been said above of boring and blasting refers only to _downright_ or vertical bores; but, in the lower parts of a quarry, it is often necessary to have recourse to what are called _breast-bores_, from their running in a nearly horizontal direction and piercing the front or breast of the rock. Those bores are not so easily made as the _downright_ bores and, in general, are only used where the rock is low, or in taking up bottom rock. They can seldom be carried to a greater depth than about 9 or 10 feet, owing to the difficulty of turning the jumper, and can never be bored quite horizontally, but require as much dip as will retain a little water in the hole to keep the jumper moving. Instead of throwing the mass outward, as is done by _down-bores_, those _breast-bores_ generally only cut or break the stone in the direction or line of the bore, so that the block always requires to be afterwards removed by _bulling_, in the manner already described. ~Dressing of the Lighthouse blocks.~ The dressing of the blocks for the Lighthouse Tower, as already mentioned, was one of the most important operations in the workyard at Hynish; and as no writer with whom I am acquainted has given any account of the mode now practised of dressing granite, I hope I shall be excused for attempting, in this place, to give some idea of the method employed by the masons of Aberdeenshire, whose skill in that department of workmanship is well known both in our own and in other countries. As the whole of the materials for the Tower were to be dressed in such a manner as to avoid the necessity of any fitting on the Rock, by the introduction of what are technically called _closers_, the greatest accuracy in the formation of the moulds from which the stones were to be shaped became necessary. With that view, I had a _trainer_ or _radius_ made with a moveable _vernier_, capable of sliding along it, so as to give the differences between the _readings_ of the feet, as far as to the _thirtieth_ part of an inch; and I was thus enabled to lay off the _batter_ or slope on each course (according to the quantities in the Table of Co-ordinates in the Appendix) with great nicety, and so to trace very distinctly the contour of the intended column.[22] On the stone floor of an apartment in one of the workshops, the _quadrant_ of each course of the building was carefully drawn out, at full size, and divided into the sectors which were required for preserving a due _bond_ among the joints of the adjoining courses. The form of each stone in the tower having been thus determined by those full-sized draughts, moulds, representing the _beds_ and _sides_ of each stone, were prepared according to them, of seasoned timber, well shielded at the angles with sheet-iron, to prevent their being injured. Those moulds having been marked with reference to the number of the course, and the position of the stones in the wall, were given to the foreman of the workyard, who regulated