It is of some consequence, in the first place, to know that the introduction of steam-machinery has added to the accuracy of clockwork and at the same time considerably diminished its cost; fifty or sixty years ago there would have been charged as much as £800 for a turret clock inferior to that which may now be procured for £150; and the result is to be seen in the largely increased numbers of public time-pieces. It is obvious, however, that there is none the less need of care in the choice of a Clockmaker, for upon his skill and trustworthiness will depend whether the money be well spent or not, and whether the instrument furnished by him prove to be valuable and serviceable. It is not a purchase wherein the buyer can usually of himself judge of the merits of his bargain, he must rely upon the reputation established by previous works of the same kind. If the Clockmaker be not merely a clock-seller (as is too often the case, for Turret Clockmakers are but few), he will be able to point to similar instruments made and set up by himself in different towns and cities, in proof of his ability, but there will still be a necessity for explaining to the purchaser the chief points upon which the accuracy of such a time-keeper must depend. In the first place, it is necessary to say that Turret Clocks are not merely house clocks upon an enlarged scale, differing from the latter merely in size and weight, but that the extra strength of the machinery requires greater weight of materials 'in a ratio as much higher as the cube is higher than the square of any of its dimensions,' and that increased weight means increase of friction. Besides this point which is peculiarly the province of the Turret Clockmaker, there are important questions to be considered by architects and their employers as to the proper method of constructing a Turret Clock chamber, so as to prevent too much atmospheric variation,--heat and cold, wind and damp, being each likely in some degree, as the seasons change, to affect the public time-keeper,--as witness the clock of St Paul's Cathedral, popularly believed to be an exemplary piece of mechanism, and yet often forced by the wind to vary its time so as to damage its own reputation among those who narrowly watch its behaviour under what may be called trying circumstances. It is not wise to build a tower without careful consideration for the tenant which is to occupy it, or having regard merely to architectural notions of external proportion, for usually it happens that when clock and bells occur as an afterthought, there is often some difficulty and extra expense in planning the room for them. Plenty of length and breadth to allow of the proper fall of the clock-weights and the swing of the pendulum save much in the cost of fixing, and are necessary to secure good time-keeping with the least trouble, for it is obvious that where numerous bevelled wheels with rod-work are employed for the