The supply of water necessary both for the protection of this enormous building from fire, and for the use of fountains and machinery to be exhibited, is furnished at a very liberal rate by the Chelsea Waterworks' Company. It is brought into the building by a 9-inch main pipe, at about the centre of its length, branching out into three 6-inch pipes, which extend throughout the whole length of the building. Short pipes branch off from these, terminating in fire-cocks, placed at such distances that a circle of 120-feet radius from any one of them will touch a similar circle described round the adjacent ones; by which means the whole extent of the building may be brought under the action of hose attached to each of the fire-cocks. The water is supplied at a pressure equal to a column of about seventy feet, so as to work the fountains that will be exhibited, and to play efficiently from hose in case of any accident by fire. The quantity which the Company have undertaken to supply is 300,000 gallons a day. The Stability of the Building. The subject of the strength and stability of the building is one on which considerable anxiety has been felt, both by the public at large and by those professional bodies more capable of forming a correct judgment upon it. In the prolonged discussion which followed the reading of Mr. Wyatt's paper at the Institution of Civil Engineers, many points of objection were raised which seemed at first sight of a very serious nature; but, in most cases, the answers that were given to them were perfectly satisfactory. The two greatest difficulties raised were, firstly, the enormous surface presented by the exterior to the pressure of the wind, with apparently but a slight power of resistance; and, secondly, the construction of the galleries, which, it was thought, would not be able to resist the vibratory motion likely to be produced by great numbers of people walking upon them. The results of several calculations were adduced on the occasion alluded to in support of the objections on the first point; but perhaps the best answer that could be given to them was the circumstance mentioned by Mr. Fox--that on the 5th of that month (January) the pressure of the wind, which blew a perfect gale, was not only much above the average, but very nearly reached the greatest amount known within a considerable period in London--about 25lbs. per square foot; and that as the building, although in an incomplete state, had resisted that pressure without receiving any injury, it was fair to conclude that, when finished, it would be able to sustain the greatest force which the wind could be reasonably expected to exert upon it.