Testing the Gallery Floor.
View of the Boiler House.
"For this purpose a very ingenious apparatus was devised by the late Mr. Field, President of the Institution of Civil Engineers, for testing the stability of the galleries in situ, and on being applied over the greater part of the building not a single bolt or girder gave way under its action. This apparatus consisted of eight square wooden frames divided into thirty-six compartments, each just capable of containing and allowing to rotate a 68-pounder shot. The surfaces of the balls placed in each of these compartments came in contact with the gallery floor, the frames themselves being attached to one another and running along the floor by means of castors fixed at the angles; the whole apparatus being drawn along by a number of men. Two hundred and eighty-eight 68-pound shot confined in a limited area were thus set rolling over more than half the extent of the galleries; when, not the slightest mishap having occurred, the experiment was considered decisive, and a persistence in it deemed unnecessary."
The pressure obtained in this experiment amounted to about a hundred pounds per square foot, and it had been ascertained that the greatest pressure caused by packing men together as closely as possible was equal to about ninety-five pounds per square foot; so that the testing force applied was considered amply sufficient, as a considerable portion of the surface of the gallery will be occupied by light articles exhibited in the cases and stalls which are placed along the centre of the gallery, where a great weight would have most effect.
This ingenious method of proving the strength of the galleries in situ, without endangering those engaged in the experiment, is admirable; and the result of the proof will no doubt allay all fear in the mind of the public as to the safety of this portion of the building.
T is always much easier to point out the defects of any work than its excellences; whilst we may, therefore, safely leave the former, as regards our present subject, to be discovered and enlarged upon by those who may be perhaps more competent than ourselves, we will attempt to point out what we conceive to be some of the advantages obtained in the present building.
One of the principal of these, considering throughout the purpose of the structure, is, perhaps, the uninterrupted view of the interior which the spectator may obtain from any point of the building—a matter of great importance to the general grandeur of its effect. From the galleries more particularly, which will be less obstructed by large objects, the eye of the spectator will be able to range from end to end of the vast edifice; while the transparency of the material used for the roof allows every object to be brilliantly illuminated. The slender lines of the supports, though they serve to sustain a protecting covering, scarcely interrupt the view of the objects protected, and the absence of any fixed divisions or partitions enables all the articles exhibited to be so arranged as to suit the peculiar requirements of each particular class; while the ample space between the supports has admitted of the formation of large open avenues for the free passage of visitors, who may thus reach as readily the remotest corners of the building as those situated near the entrances; and whenever the visitor may find himself fatigued by the labour of sight-seeing, he will be sure to find himself near one of the numerous exit-doors, whereby he may immediately free himself from the crowd of spectators.