62

CONSTRUCTION OF THE BUILDING,

long edge of the glass. The sash bar is then brought down and secured at thetop to the ridge, and at the bottom to the edge of the gutter; the lower edge ofthe glass bedding on putty about three-quarters of an inch wide. A slight blow tothe lower end brings the upper edge of the glass home into the groove in theridge. The glass being then pressed down, the putty is made good in the groovesexternally, and by the repetition of this simple operation, the essentials of thissystem of roofing are constructed.

Lightness one of One among the many advantages of Mr. Paxton’s roofing is its extreme light-er. In the instance of that of the Exhibition Building, the whole of the

roofing. roofing ("the weight of the trusses that support it being of course deducted),

weighs only lbs. per foot superficial upon the average.

In order to mitigate the intensity of the light, and at the same time to assistThe canvas cover- in keeping the building cool, a canvas covering has been provided, extending overthe entire area of the flat roof. The canvas is attached to the ridges, and allowedto hang down between them in a festoon. As one width of canvas is insufficientto reach from ridge to ridge, two are sewn together, the seam occurring in thecentre, immediately over the Paxton gutter. The rain descending falls on theits uses. canvas, and clings to it by capillary attraction, creeping down until it arrives

at the seam, where it passes through the canvas, and falls into the Paxton gutter ;thus the danger of the passage of water which might take place through brokenpanes or imperfect putty-joints, is obviated, and the chances of leakage are con-sequently materially diminished.

The flooring;, In order to trace continuously the course of the vertical supports from the

ground to the roof, we have not interrupted our description by detailing thenature of the flooring; but as that is one of Mr. Paxton’s ingenious con-trivances, it would not be right to allow it to pass unnoticed. In a paper, readby Mr. Paxton at the Society of Arts , on the 13th of "November, 1850, thatgentleman narrated the experiments which led to the origination of the presentdesign, and stated that he had tried many methods, in order to find out themost suitable floors for the pathways of horticultural structures. After enume-rating the objections to the use of stone and close boarding, he mentioned,that “he had ultimately been led to the adoption of trelliced wooden pathways,“with spaces between each board, through which, on sweeping, the dust at once« disappears, and falls into the vacuity below.” He thus describes his applicationof these experiments to the Exhibition Building:—as described by “Whilst the accomplishment of this point” (the speedy removal of dust)“ was most important in plant-houses, I consider it doubly so with respect to the“ Industrial Building, where there will be such an accumulation of articles of“ delicate workmanship. Before sweeping the floors of the Great Building, the“ whole will be sprinkled with water from a movable hand-engine, which will be“ immediately followed by a sweeping-machine, consisting of many brooms, fixed“ to an apparatus on light wheels, and drawn by a shaft. By this means a large“ portion of ground will be passed over in a very short space of time.” Theboards for the floor are H inch thick, laid half an inch apart, upon joists 7 inchesby 21 inches, which rest upon large timbers or sleepers, 13 inches by 3i inches,at intervals of 8 feet apart. Through the interstices left between the boards thedust passes, and the merits of this system of flooring are thus summed up byMr. Paxton “ It is very economical, dry, clean, pleasant to walk upon, admits“ of the dust falling through the spaces, and even when it requires to be