The plan forms a parallelogram, 1,848 feet long and 408 feet wide, besides a projection on the north side, 48 feet wide and 936 feet long. A main avenue, 72 feet wide and 66 feet high, occupies the centre through the whole length of the building. Flanking this on either side are smaller avenues alternately 24 feet and 48 feet wide; the two first on either side of the centre are 43 feet, and the remainder 23 feet high. About the centre of the entire length, at a point determined by the position of a row of large trees, which it was resolved to inclose, these avenues are crossed by a transept of the same width as the main avenue, or 72 feet, and 108 feet high; two other groups of trees on the ground give occasion for open courts, which are inclosed within the building. The area thus inclosed and roofed over amounts to no less than 772,784 square feet, or about 19 acres;[4] the building is, therefore, about four times the size of St. Peter's at Rome, and more than six times that of St. Paul's, London. Three entrances lead to this vast interior, one in the centre of the principal or south front, and one at either end of the building. The number of these is necessarily small, in order to facilitate the arrangements for the money-taking, and to avoid having too large a staff of officers; on the other hand, it was equally desirable to afford the most ample opportunities of egress for visitors, and accordingly fifteen exit doors are placed at frequent intervals. GROUND-PLAN OF THE BUILDING. [Illustration] A. Principal Entrance. B. West Entrance. C. East Entrance. D. Refreshment Courts. E. Entrance. F. Gentlemens' Ante-rooms. G. Ladies' Ante-rooms. H. Pay Place. I. Accountant. K. Exits. L. Ante-rooms. M. Committee Waiting-room. N. Royal Commission. O. Clerks. P. Stairs. Q. Engine House. It will be well to mention here that the horizontal measure of 24 feet, which we have seen as the unit in the plan of the Building Committee, is also preserved in the present plan; every horizontal dimension of which is either a certain number of times or divisions of twenty-four feet.