The coolness thus obtained within the Palace will be sought in vain on such a summer’s day outside the edifice. The total length of columns employed in the construction of the main buildings and wings would extend, if laid in a straight line, to a distance of sixteen miles and a quarter. The total weight of iron used in the main building and wings amounts to 9,641 tons, 17 cwt., 1 quarter. The superficial quantity of glass used is 25 acres; and weighs 500 tons; if the panes were laid side by side, they would extend to a distance of 48 miles; if end to end, to the almost incredible length of 242 miles. To complete our statistics, we have further to add that the quantity of bolts and rivets distributed over the main structure and wings weighs 175 tons, 1 cwt., 1 quarter; that the nails hammered into the Palace increase its weight by 103 tons, 6 cwt., and that the amount of brick-work in the main building and wings is 15,391 cubic yards. From the end of the south wing to the Crystal Palace Railway station, as above indicated, is a colonnade 720 feet long, 17 feet wide, and 18 feet high. It possesses a superficial area of 15,500 feet, and the quantity of iron employed in this covered passage is 60 tons; of glass 30,000 superficial feet. But vast as are the proportions of the Crystal Palace, novel and scientific as is the principle of construction, we are in some degree prepared for this magnificent result of intellect and industry by the Great Exhibition of 1851. One arrangement, however, in the present structure admits of no comparison; for, in point of extent, it leaves all former efforts in the same direction far behind, and stands by itself unrivalled. We refer to the process of warming the atmosphere in the enormous Glass Palace to the mild and genial heat of Madeira, throughout our cold and damp English winter. The employment of hot water as a medium for heating apartments seems to have been first hinted at in the year 1594, by Sir Hugh Platt, who, in a work entitled “The Jewel House of Art and Nature,” published in that year, suggests the use of hot water as a safe means of drying gunpowder, and likewise recommends it for heating a plant-house. In 1716, Sir Martin Triewald, of Newcastle-on-Tyne, proposed a scheme for heating a green-house by hot water; and a Frenchman, M. Bonnemain, a short time afterwards invented an apparatus for hatching chickens by the same means. In the early part of this century Sir Martin Triewald’s plan of heating was applied to conservatories, at St. Petersburgh; and a few years later, Bonnemain’s arrangement was introduced into England, where it has undergone several improvements, and occupied the attention of scientific men. The application of hot water to the heating of churches, public libraries, and other buildings, has been attended with considerable success, and it is now looked upon as the safest, as well as one of the most effectual artificial methods of heating.