NATURAL HISTORY BUILDING 27 



the driveway in front of the lowest step is +23.92, while that of the 

 portico floor, forming the upper step, is +34, making the total rise 

 aboat 10 feet. The distance in a horizontal line from the edge of 

 the lowest step to the outer edge of the portico floor is 52 feet 5^ 

 inches. 



The upper dies measure 12 feet 6 inches deep by 11 feet across and 

 their tops line with the floor of the portico. The distance between 

 them is 45 feet 1^ inches, which is the length of the steps in this series 

 except the lower four which are longer and return against the dies. 

 The lower dies, which are 11 feet deep, 20 feet across the front and 

 6 feet 7f inches high above grade, are 123 feet apart. All of the 

 steps of this run are of that length with the exception of the lower 

 two, which also extend a short distance on to the outer faces of and 

 return against the dies. All steps are 18 inches wide, except the bot- 

 tom one in each run which is 20 inches. The rise is 5 inches with a 

 wash of ^ inch. The dies, in their shape and position, have been 

 planned to serve as pedestals for sculpture groups, and each is sur- 

 mounted by a low plinth. 



The outer ends of the intervening platform are in plan quadrants 

 of a circle, with an extreme radius of 31 feet 4 inches, swinging out- 

 ward from the upper to the lower die on each side. Completing and 

 concentric with these curved ends on each side is a massive granite 

 seat or bench, which is raised above the platform level by two steps. 

 These seats, which are cut in several sections each from a single block 

 of stone, stop 6 inches short of the flanking dies and terminate in an 

 arm at each end. The extreme width of the platform, including the 

 seats, is 139 feet 4 inches; while its depth from one run of steps 

 to the other is 22 feet 1^ inches. The platform is laid in a panel 

 design, having across its depth three rows of square panels, separated 

 and bordered by bands of pink New Jersey granite. On each side, in 

 front of the lower curved step leading to the seats, is an ornamented 

 border each alternate stone of which has a perforated design. The 

 perforations, extending entirely through the stones, give outlet for 

 the water from the platform, which is crowned and built to drain 

 toward them. The steps, like the platform, are cut with a rise or 

 crowning surface from the ends to the center, the greatest rise, 

 namely, 3 inches, occurring in the bottom step. 



From the outer ends of the platform on each side a finished 

 granite retaining wall preserving the same curvature is carried down 

 to the level of the grade of the basement area. The original plan 

 contemplated a granite retaining wall, surmounted by a balustrade, 

 starting from the lower dies of the approach and facing the southern, 

 eastern and western fronts of the building, but its expense was 

 greater than could be met from the appropriation and in its stead 

 the embankment has been sloped and sodded. 



