DEPARTMENT OF TERRESTRIAL MAGNETISM. 301 



As heretofore, all of the non-magnetic castings were made in our own 

 foundry under the direction of Mr. C. Huff. During the year over 

 3,500 pounds of strictly non-magnetic castings, including bell-metal, 

 copper, gun-bronze, red and yellow brass, and speculum, were made. 

 Mr. Huff also designed the electric installation on the Carnegie, and de- 

 signed, as well as constructed, the switch-boards for the Carnegie and 

 for the experiment building. 



The personnel of the instrument shop consisted of Messrs. C. Huff, 

 G. H. Jung, W. F. Steiner, instrument-makers; A. Smith, carpenter and 

 pattern-maker; and J. G. Lorz, apprentice in instrument-making. 

 The quantity and quality of the work turned out is sufficient evidence 

 of the activity of the working force during the year. 



BUILDING WORK AT WASHINGTON. 



The preliminary plans of the proposed Experiment Building for the 

 special investigations in magnetism of the Division of Experimental 

 Work were given some consideration in January and February 1919. 

 The requirements were (a) unusual rigidity and strength, (6) non- 

 magnetic construction, and (c) insulation against sudden temperature 

 changes. It was decided to adopt a concrete double-wall construction, 

 using brass reenf or cement, with a continuous, insulating, dead-air 

 space 2.5 inches thick between the two 6-inch walls; further heat insula- 

 tion was provided for by double windows and double doors, and by a 

 double ceiling of plaster-board, inclosing a 10-inch dead-air space 

 between purlins and a 1-inch dead-air space between the two layers 

 of plaster-board on the under side of the roof purlins. A site was 

 selected, recommended, and approved in March. Thirteen drawings, 

 covering the details of the building, special electric installations with 

 special switch-boards, switch-board extension in the main laboratory, 

 and various pipe-lines, were completed in April, and bills of materials 

 were drawn up. 



Because of the unusual requirements and specifications particularly 

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

 contracts for the work, which had therefore to be undertaken by the 

 Magnetic Survey Division. It was impossible even to secure bids for 

 the mill- work, all of which had to be done in our own shop. The rough 

 grading and installation of rain-water drains and connections to the 

 culvert were completed and the finished concrete foundations and floor 

 were in place by April 26. The concrete walls were started March 12 

 and completed June 14. The steam heating is provided from the main 

 laboratory, the heating plant having been suitably enlarged. Special 

 tests showed that it would be necessary, because of non-magnetic 

 requirements, to use brass pipe in the Experiment Building and to a 

 point not less than 40 feet from the nearest part of it. The radiators 

 are made of brass pipe. The necessary steam, return, gas, hot and cold 



