[ 23 J 68 



blue gneiss, of good shape and size, laid on the natural bed, and \re{! 

 bonded to the face work. Behind the outside walls, and at a distance of 

 four inches from them, a five-inch bricli wall, tied to the outer wall by 

 at least one bond stone in every three feet square, will be laid. This 

 backing will be returned, to meet the front wall at all the jambs and 

 arches of all the windows and doors. It will also be tied to the front 

 walls, in the piers between the windows, by brick cross walls nine inches 

 thick, to form the flues ; which flues will be constructed as follows : 

 In each of the piers between the windows there will be three flues 8 

 by 16 inches in the clear inside, which will be carried from a point three 

 feet below the underside of the beams of the first story to the top of the 

 building. One of these flues will be connected with the furnaces by a 

 horizontal flue of galvanized iron^ or double-cross tin, two feet square, 

 which will be furnished by the contractor, for the purpose of diflnsing 

 the hot air throughout the building. All these flues v/ill have neat regis- 

 ters in the rooms, for the proper regulation of the heat. The second 

 flue will have an opening in each story, on the line of the ceiling, on 

 the outside of the wall, and another opening into the bases of the rooms 

 inside: these will admit the cold air from the outside of the buildina- 

 into the respective rooms for the purpose of proper ventilation, and will 

 be closed up on the level of the floor of each story, by a cross wall 

 over the outside opening; and each of the above flues will be fur- 

 nished with a heavy sheet-tin slide valve, with proper fixtures for open- 

 ing and shutting, placed in such part of the flue, and made in such 

 manner, as may be directed by the architect. 



The third flues will have openings on the inside on a line with the ceil- 

 ings of all the rooms; through tliese the foul and heated air will be car- 

 ried off and discharged by an opening under the coping of the building. 

 All these flues will be furnished with two sheet-tin valves each, made 

 and placed in the manner directed by the architect. Proper flues^ welt 

 parged, will be carried up for the furnaces, fireplaces, engine; laboratory^ 

 &c., in such places as may be directed bj' the architect. 



In addition to the above ventilating flues, openings with valves will 

 be foymed in all the groined ceilings^ which will be connected with the 

 corner towers and flues in the larger towers. 



Thickness of tvalls. — The thickness of the walls of the main building 

 above the water tables will be two feet six inches in the first story, and two 

 feet in the second story, exclusive of all projections of the buttresses, cor- 

 bel courses, battlements^, bands, (kc. 



The thickness of the end walls of the main building will be two feet 

 six inches for a height of fifteen feet above the line of the water table^ 

 and for the remaining portion two feet, exclusive of all projections. 



The thickness of the walls of the connecting ranges above water table 

 will be twenty-two inches, exclusive of all projections. 



Th© thickness of the clerestory wall of the west range will be sixteen 

 inches, and it will be backed in with good hard brick. 



The thickness of the walls of both" wings will, above the water table, 

 be two feet, exclusive of all projections and the batter at the base of the 

 east wing. 



The thickness of the walls of central front towers will be three feet 

 six inches in the first stories, three feet in the second story, two feet six 

 inches in the third story, with the corners filled in to aid in'supporting the 



