Non-Magnetic Experiment Building :'>">: 



Because of the requirement of non-magnetic construction, the reinforcement material 

 used throughout for the concrete was of brass wire and brass rod; all necessary tie-bolts, 

 lag-screws, tie-rods, nails, and hardware were of brass or bronze. The detailed cross- 

 section (see Fig. 3) will serve to indicate the general character of the reinforcement. 



The 13 drawings covering the details of the building, special electric installations 

 with special switchboards, necessary switchboard extension in the main laboratory, 

 various pipe-lines and outlet arrrangements, laboratory tables, and heating arrangements 

 were completed in April 1919. The insulation against temperature changes within the 

 building provided by the continuous, insulating, dead-air space between the two 6-inch 

 walls was further increased by provision of double windows and double doors, by a double 

 ceiling of plaster-board, 1 inclosing a 10-inch dead-air space between purlins, and by 

 a 1-inch dead-air space between the two layers of plaster-board on the underside of the 

 roof purlins. 



Because of the unusual requirements and specifications, particularly those for 

 non-magnetic construction, it was not possible to secure reasonable contracts for the 

 work, which had, therefore, to be undertaken by the Department, and the author was 

 assigned by the Director to take charge of the construction. It was impossible even to 

 secure bids for the mill-work, all of which was special and had to be made in the wood- 

 working shop of the Department. The rough grading and installation of rain-water 

 drains and connections to culvert on the grounds were completed and the finished concrete 

 foundations and floor were in place by April 26. The wide heavy footing-courses and 

 the 3-inch concrete sub-floor were placed first and then waterproofed with 4 layers of 

 felt and pitch, according to the specification given later, before the placing of the 6-inch 

 thick concrete top floor. The 1-inch finished cement surface to the floor was cast at the 

 same time as the top floor, thus obtaining the advantage of an additional inch of thick- 

 ness in the structural strength of the concrete. The footings and concrete floor were all 

 on original excavation, there being no fill under any of the floor or footings. The con- 

 crete walls were started March 12 and completed, including both gable ends to the ridge 

 of the roof, by June 14. 



The sill course around the building, the sills under the windows in the gable ends, 

 and the columns and pilasters at the entrance were all made of concrete and cast in place, 

 with fine granite-and-mica surfacing; the forms used in casting them were moved 

 immediately after casting and the excess of white cement used in the surface treatment 

 removed by water spray, thus bringing out the small granite-and-mica chips and producing 

 an artificial stone having much the appearance of granite. The outside stucco finish 

 above the sill level was of Portland cement stucco applied in three coats in accordance 

 with the recommended practice for Portland cement stucco issued by the American 

 Concrete Institute's committee on the treatment of concrete surfaces. 2 The aggregate 

 of the surface finishing coat consisted of yellow sand, white Portland cement, and large- 

 size, granite-and-mica chips so treated with water spray as to remove the film of cement 

 and sand from the coarse aggregate. All of the granite and mica used for this work was 

 tested and found to be non-magnetic. The color effect of this stucco finish harmonizes 

 well with the general color scheme of the other buildings on the grounds. The interior 

 of the building is plastered in hard sand finish, a pleasant buff color having been obtained 

 by use of a yellowish sand in the final coat. 



Because of the scarcity and excessive cost of materials it was necessary to substitute 

 for the slate roof, as originally specified, a roof of felt shingles saturated and waterproofed 

 with asphalt and covered with crushed natural slate of dark soft red color. This roof 



1 The board known as "sheetroek" was used; it is about three-eighths inch thick and is practically pure gypsum cast 

 between heavy card-boards. 



2 Proceedings, American Concrete Institute, vol. 15, 1919. 



