24 UNITED STATES NATIONAL MUSEUM 



column-supported construction across the entire face forming the 

 elaborately decorated portico described below. 



The openings in the masonry for the large semicircular windows 

 have an extreme radius of 20 feet 4 inches to the inner edge of the 

 archivolt. In the jamb and at the sill there is a rebate 11 inches 

 wide, by which the opening is reduced in area to less than that of a 

 semicircle of 19 feet 5 inches radius. The archivolt is 4 feet wide, 

 is divided into 27 voussoirs, and has a sunken panel face and molded 

 inner and outer edges. Each opening is divided by two granite mul- 

 lions, 3 feet 2 inches wide, into three sections, of which the middle 

 section is slightly wider than the lateral ones at their base. The 

 window area in these sections is subdivided by a lattice pattern into 

 triangular lights. The framework is constructed of sheet copper, 

 reenforced where necessary to provide proper stiffness, and the sills 

 and spaces in the frames are filled with concrete. The glass is plate, 

 ground on the inner surface. 



In the ground story, where the south projection amounts to 27 feet 

 5| inches and is 80 feet 2 inches wide, the side walls are of the 

 Milford granite, but above the first floor level the stone work is en- 

 tirely of the Bethel granite, laid in regular courses 2 feet wide except 

 as architectural or decorative features have necessitated a different 

 treatment. 



The rotunda construction of the interior is carried through the 

 roofs of the pavilion in the form of a circular drum, 84 feet in diam- 

 eter, also faced with Bethel granite in 2- foot courses to a height of 

 1 foot above the ridges of the pediment roofs. The upper 6^ inches 

 of the next course carry the lower member of a 3-foot 5|-inch metope 

 and triglyph-decorated frieze, which is followed by a denticulated 

 cornice, 4 feet 4| inches wide. Above the cornice the remaining 

 granite work consists of a capped parapet 4 feet 1| inches high, and 

 three courses of stone aggregating 4 feet 2f inches in height, each of 

 these crowning courses being stepped back to the extent of about its 

 own height on the course below. The top of the upper course is 

 17 feet f inch above the parapet blocks of the four faces, and 118 feet 

 10^ inches above the first floor level. 



The slate-covered dome, the construction of which is described in 

 another connection, is a spherical segment 75 feet in diameter at its 

 base and 21 feet 8 inches high above the upper edge of the drum. 

 The top of the curb around the eye at its crest is the highest masonry 

 work of the building, being 142 feet 2^ inches above the first floor 

 level and 165 feet 2| inches above the grade level of the building. 



PORTICO 



The portico, which is singularly effective and imposing, is in archi- 

 tectural treatment of the Roman Corinthian order, its main features 



