EXHIBITION, BRITISH INDUSTRIAL. 



415 



point the ribs of the roof are seen from end to 

 end in fine perspective. 



The eastern Annexe is exactly similar to the 

 rn in its construction; but it is 200 feet 

 shorter. 



The Interior. Entering east or west, the 

 ascent is by two steps until the level of the 

 dais under each dome is reached. From either 

 point the interior of the whole building may be 

 seen in one view, at 6 feet above the rest of 

 the floor. Thence three flights of steps, 80 feet 

 wide, lead into the nave and transept on either 

 side. 



The supports on either side of the nave (800 

 feet long and 100 feet high) consist of square 

 and round cast iron columns, coupled together; 

 the former carry the gallery floor, and the 

 latter, advancing into the nave, receive the 

 principals of the roof. From the capitals of 

 the columns spring the roof frames, which con- 

 sist of three thicknesses of plank, from 18 in- 

 ches to 2 feet 6 inches deep, firmly nailed and 

 bolted together, and so arranged that their ends 

 break joint. The centre plank is 4 inches 

 thick, and each of the outer ones is 3 inches ; 

 the lower edges are tangents to an imaginary 

 semicircle, round which they form half of a 

 nearly regular polygon. From the springing 

 rise the posts of the clerestory windows, 25 

 feet high. The principal rafters of the roof 

 frames rise from the top of these posts, and are 

 carried up, after passing a tangent, to the back 

 of the arch, to meet at the ridge in a point 25 

 feet above the top of the clerestory. The 

 angles over the haunches and crown of the 

 arch are firmly braced together, so as to reduce 

 the thrust as much as possible. 



The rib is repeated thirty times in the length 

 of the nave, and from its graceful curve and 

 lightness it produces a fine eftect. Between 

 every roof principal is a clerestory light 25 feet 

 high, consisting of three arches springing from 

 intermediate mullions. The roof is covered 

 wjth felt and zinc on l|-inch planks. The 

 transepts run from each end of the nave, at 

 right angles to it, and extend north and south 

 650 feet ; they are the same width and height 

 as the nave, and the ribs of its roof are of the 

 same construction. 



Construction. The principals were placed in 

 the nave roof. This was done by a huge move- 

 able scaffold. One half of a rib was first hoist- 

 ed to its place; when in position, the other 

 half was raised ; and as soon as both were fixed 

 true, they were joined together by completing 

 the arch and bracing over its crown. 



The hoisting was all done by a hoist, con- 

 nected with a portable steam engine. 



The galleries form an abutment to the nave 

 and transept roof. As the roof thrusting out- 

 ward tends to throw the columns out of the 

 p*pendicular, this is counteracted by strong 

 iron braces anchored to the foundation of the 

 inner column, and carried up to the top of the 

 opposite outer column. Another bracing, 

 anchored to the footing of the outer column, is 



carried np to the top of the inner column, to 

 secure it from being acted on by the force of 

 the wind. This vertical cross-bracing is re- 

 peated at every hundred feet, or every fourth 

 bay, and by introducing horizontal diagonal 

 bracing under the roof flats, they are turned as 

 it were into a deep horizontal girder, supported 

 at two ends by the columns vertically braced 

 as just described. This horizontal girder there- 

 fore takes the thrust of the three intervening 

 ribs. 



The whole structure may be separated into 

 three classes of work that which is meant to 

 be permanent, viz., the front facade and the 

 narrow strips of brick buildings at both wings 

 running north and south; that which is quasi 

 permanent, viz., the naves, transepts, domes, 

 and covered courts and galleries; and that 

 which is absolutely ephemeral, in the Annexes, 

 and the refreshment rooms over the arcades at 

 the south end of the Horticultural Garden. 

 Standing at the centre of the front in Crom- 

 well road, we have the front building of 1150 

 feet 9 inches extreme length stretching right 

 and left, with a general width of 50 feet, and 

 two stories in height. At the centre are the 

 grand entrance hall, vestibule, and within 

 these, to the right and left, the grand stair- 

 cases leading to the higher floor ; returning 

 southward we enter a hall of 150 feet in 

 length, for sculpture chiefly, and as a vestibnle 

 to the great ranges of picture galleries to the 

 east and west, and extending on into the wing 

 tower buildings to a total length of about 500 

 feet each way. 



The appropriation of the several portions of 

 the building is briefly thus: the nave, tran- 

 septs, galleries, and courts for the display of 

 general industrial productions ; the brick build- 

 ing on the north, inclosing the narrower courts, 

 for refreshments ; the grand picture gallery ex- 

 tends along the south, and has auxiliary wings 

 in front of the east and west transepts extend- 

 ing their whole length ; these picture galleries 

 requiring to be lighted from the top, are placed 

 above the entrances, which on the south side 

 stretch to either hand for the display of car- 

 riages, &c. 



.Decoration of the Building. This cannot be 

 better described than by Mr. Grace, who, in 

 April, 1862, read before the Society of Arts a 

 paper in which he informs us that it was the 

 23d January last when he received his authori- 

 ty to proceed with the decoration, and it was 

 to be all completed by March ; that is to say 

 some twenty acres decoratively painted in 

 about eight weeks. 



" After careful consideration I decided that 

 the general tone of the roof must be light, and 

 that the best color would be a warm pale gray ; 

 that the arched principals must be made to 

 stand out clear from the roof: that they must 

 look well in a perspective of 800 feet ; and that 

 they must not look heavy or confused as they 

 approached each other in the distance. The 

 form of these is polygonal, and in three thick- 



