102 ANNUAL OF SCIENTIFIC DISCOVERY. 



behind, from which they are afterwards detached by hand. During 

 the operation, a squirt-pump throws out a jet of water between each 

 pair of scalpels, to prevent the heating- of the tools, and to wash out 

 the rubbish. After their complete separation, the blocks are pulled 

 out by the help of the endless cable, and received in a wagon, to be 

 drawn from the tunnel. The machines are only to cut a gallery 13 

 feet wide and 7 feet high, which is afterwards to be enlarged by the 

 ordinary means to the size mentioned above. It has already been 

 ascertained that each of the two machines, at the opposite ends of the 

 tunnel, will excavate to the extent of 22 feet per day, and it is to be 

 estimated that the whole excavation will be completed in four years. 

 The rocks which it is supposed will be met with are gypsum, lime- 

 stone, and quartz in veins. 



BUILDING FOR THE EXHIBITION OF 1851. 



AT the meeting of the Society of Arts, on Nov. 13, Mr. Paxton, 

 the architect and designer of the building for the exhibition of 1851, 

 gave an account of that structure. Mr. P. is chief gardener of the 

 Duke of Devonshire, and under his care several conservatories of 

 enormous size have been erected, and the building for the exhibition 

 is, in general, a mere expansion of the idea followed in them; so 

 much so, that it was designed and planned in ten days. Not a particle 

 of stone, brick, or mortar is necessary to be used. The building is 

 1,851 feet long, and 456 feet broad in the widest part. It covers more 

 than 18 acres, and the whole is supported on cast-iron pillars, united 

 by bolts and nuts, fixed to flanges turned perfectly true, and resting on 

 concrete foundations. The total cubic contents are 33,000,000 feet. 

 The six longitudinal galleries, 24 feet wide, running the whole length 

 of the building, and the four transverse ones of the same dimensions, 

 afford 25 per cent, additional exhibiting surface to that provided on the 

 ground-floor. In order to give the roof a light and graceful appear- 

 ance it is built on the ridge and furrow principle, in which, instead of 

 rising in a regular slanting direction to one ridge or apex, it is com- 

 posed, as it were, of several small roofs, the apices of which are on a 

 level. It is glazed with plate-glass. The rafters are continued in 

 uninterrupted lines the whole length of the building. The transept 

 portion, although covered by a semicircular roof, is also on the angu- 

 lar principle. All the roof and upright sashes are made by machinery. 

 The length of sash-bar requisite is 205 miles. The quantity of glass 

 is about 900,000 feet, weighing upwards of 400 tons. The lower tier 

 of the building, however, will be boarded with fillets, planted on in a 

 perpendicular line with the sash-bars above. By means of gutters of 

 a peculiar construction, rain-water is conveyed to the hollow columns, 

 and thence to the drains below. The floor consists of trellised wooden 

 pathways, with openings between the boards, into which the dirt can 

 be swept, so as to fall into the empty space below. Ventilation is ob- 

 tained by making four feet round the whole of the basement part of 

 the building of louvre-boarding, and at the top of each tier a similar 

 provision of three feet is made, with power to obtain an additional 



