354 Special Reports 



harmonizes with the color detail of the Experiment Building as well as with the roofs 

 of the other buildings on the grounds and has given very good service, being in first- 

 class condition at the end of two severe winters. 



It was originally intended to place the lead-sheathed copper cables for electric 

 circuits, the pipe-lines for water, gas, compressed-air, steam, drain, and sewer in terra- 

 cotta ducts. Since, however, this would have practically prohibited access without 

 considerable expense for any necessary future repairs, and particularly for the addition 

 of new pipe-lines or electric circuits between the main laboratory and the Experiment 

 Building, a concrete-lined tunnel of inside width 20 inches and inside height 36 inches 

 was constructed between the furnace room of the main laboratory and the Experiment 

 Building. The small initial additional expense of this tunnel has already been fully 

 justified. All the pipe systems except the steam, return, and sewer connections are 

 suspended at the top of this tunnel. The various lead-covered, stranded copper-wire, 

 electric circuits are laid on the floor of the tunnel. All of the structural work, including 

 grading, inside plaster, outside stucco, mill-work, and the tunnel connection to the 

 main laboratory, was completed in October 1919. Many difficulties and delays were 

 caused by the scarcity and slow deliveries of materials and by the scarcity of suitable 

 labor under the conditions prevailing during the period of construction. 



The permanent equipment of the building, other than special instruments and 

 appliances for the investigational work, is entirely non-magnetic in character. The 

 heating is provided from the central low-pressure, steam-heating plant of the main 

 laboratory (A), about 200 feet distant. The provision of non-magnetic radiation was 

 solved by constructing in the Department shop radiators made of copper tubes 1^ 

 inches outside diameter mounted between copper manifolds top and bottom. The total 

 radiation estimated as necessary for the volume of the building was 450 square feet, 

 but so far it has been found necessary to use only 4 radiators with a total radiation of 

 225 square feet. 



As stated above, the steam, return, gas, hot-water, cold-water, drain, and com- 

 pressed-air pipe-lines and lead-incased electric cables from the main laboratory are 

 hung in the concrete tunnel. All of these lines and cables in the building, with their 

 mountings, are non-magnetic; they are also non-magnetic in the tunnel from the build- 

 ing to a point 40 feet southwest of the outside southwest corner. From that point to 

 the main building the various pipes and supports in the tunnel are of iron. The distance, 

 40 feet, was adopted after careful tests which showed that, for the number of pipes of 

 necessary sizes to be installed in the tunnel running in a north-south direction, no appre- 

 ciable disturbance of the Earth's horizontal-intensity field was experienced at that dis- 

 tance from the testing instrument. It will be readily understood that this question was 

 important from an economic point of view because of the excessive cost of brass and 

 copper piping as well as of the increased cost of satisfactorily installing such brass pipe- 

 lines. Suitable provision is made by expansion joints to allow for expansion and con- 

 traction of the steam and hot-water pipe-fines. All pipes in the tunnel, except those for 

 gas, sower, and cold water, are covered with cellular asbestos covering; the cold-water 

 fine is covered with felt. 



The provision for electric circuits consists of 10 complete circuits of No. 6 cable 

 for direct current from storage battery in the main laboratory, 1 alternating-current 

 power circuit of No. 4 cable, 1 alternating-current fight circuit of No. 8 cable, 1 alter- 

 nating-current circuit of No. 10 cable for special motor-generator, and 2 control circuits 

 for special motor-generator. Advantage was taken of the provision made for double 

 entry by placing instrument cases in the Experiment Building, on each side of the 

 entry and, accordingly, in the north and south ends of these cases, panel-boards were 

 inserted. Thus the means are provided by suitable switches, properly fused, for the 



