298 CARNEGIE INSTITUTION OF WASHINGTON. 



Construction of non-magnetic Experiment Building of the Department of Terrestrial 

 Magnetism. J. A. Fleming. Special report in Vol. IV of Researches of the 

 Department of Terrestrial Magnetism. Carnegie Inst. Wash. Pub. No. 175, 

 Vol. IV, 351-358, 1 plate, 2 text-figures (1921). 



This report gives a detailed description of the Experiment Building, de- 

 signed for special investigations in magnetism and completed in 1920. The 

 desiderata considered essential, and upon which the plans were based, 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 reinforcement, with a con- 

 tinuous insulating dead-air space 23/2 inches thick between the two 6-inch 

 walls. Further provision for protection against rapid changes of temperature 

 outside the building was provided for by double windows and double doors, 

 and by a double ceiling. The general lines of the building were made to con- 

 form architecturally with those of the Standardizing Observatory already on 

 the site. (For views of buildings see Annual Report for 1920, opposite p. 304.) 



The equipment for use of the building as a laboratory is described in detail. 

 The non-magnetic requirement made it, of course, more difficult to provide 

 suitabl}^ for heating the building, for gas, water, drain, and compressed-air 

 pipe-lines, and for the necessary electric switchboards and installations. The 

 various pipe-lines and electric cables all lead underground in a concrete 

 tunnel from the main laboratory. Provision for mounting of galvanometers 

 and other instruments was made by the use of 2-inch thick soapstone shelves 

 mounted on heavy wooden brackets built into the walls of the building. A 

 brief summary of the specifications for the construction is given. The cost 

 of construction work was about 30 cents per cubic foot of volume inclosed. 



The results of tests made in March 1920 to determine the magnetic field in 

 the completed structure show that the requirement for non-magnetic con- 

 struction was practically attained, the small linear variation in the magnetic 

 elements from the south end to the north end of the building being attribut- 

 able largely to the proximity of the main laboratory with its great mass of 

 magnetic material, and to the slightly magnetic character of the soil used in 

 grading about the outside of the building. 



Latest annual values of the magnetic elements at observatories. J. A. Fleming. Terr. 

 Mag., vol. 26, 146-149 (December 1921). 



A compilation of the most recent annual values of the magnetic elements 

 at observatories distributed over the Earth. 



Results of comparisons of magnetic standards, 1915-1921. J. A. Fleming. Special 

 report in Vol. IV of Researches of the Department of Terrestrial Magnetism. 

 Carnegie Inst. Wash. Pub. No. 175, Vol. IV, 395-475 (1921). 



This report is in continuation of the special report by Louis A. Bauer and 

 J. A. Fleming contained in Volume II of the Researches of the Department 

 (pp. 211-278). The direct comparisons of magnetic standards include results 

 at the following observatories: Agincourt, Canada; Cheltenham, United 

 States; Eskdalemuir, Scotland; Stonyhurst, England; Greenwich, England 

 (2 series); Kew, England (2 series); Honolulu, Hawaii (2 series); Hongkong, 

 China; Rio de Janeiro, Brazil (2 series); Pilar, Argentina (2 series); Apia, 

 Samoan Islands (2 series); Christchurch, New Zealand (5 series); Loanda, 

 Angola; Tananarive, Madagascar; Lukiapang, China; and Watheroo, Western 

 Australia. These direct comparisons are amplified further by indirect com- 

 parisons resulting from comparisons obtained by other organizations, in- 

 cluding particularly the following: (a) Results obtained by the superintendent 



