COMPAEISONS OF MAGNETIC STANDARDS, 1915-21 



Table 16B. Results of Horizontal-Intensity Comparisons at the Samoa Observatory, 1915. 



453 



' All I. M. S. values are referred to N; N=W +52-,. 



3 The Observatory values are based upon magnetograph data, the base-line being controlled by 4 sets of horizontal- 

 intensity determinations, the oscillation observations being made at SW and deflection observations at N during May 16 

 to 26, 1915. It is assumed that the station-difference between N and SW is negligible. 



Table 16C- Results of Inclination Comparisons at the Samoa Observatory, 1915. 



All I. M. S. values are referred to N; .V = IF + 1'.2. 



1 The Observatory values are based on magnetograph data controlled by 3 sets of inclination observations at SE 

 during May 15 to 20, 1915. It is assumed that station-difference between N and SE is negligible. 



Series II, 1921. 



Comparisons were again obtained at the Samoa Observatory in July 1921 by the 

 Carnegie party. The observations with the Observatory instruments, the same as 

 those used for the comparisons of 1915, were made by Director C. J. Westland and those 

 with the C. I. W. instruments were made by Messrs. Johnston and Grumman, under the 

 direction of Captain J. P. Ault, of the Carnegie. Some assistance in the C. I. W. work 

 was given also by Dr. H. M. W. Edmonds and by Mr. D. G. Coleman of the Depart- 

 ment's staff, the former being on special assignment to the Observatory in charge of 

 the atmospheric-electric and allied meteorological observations and the latter being 

 temporarily at Apia in the course of field work. The Carnegie instruments used were 

 C.I.W. theodolite-magnetometer No. 5 and C.I.W. magnetometer-inductor No. 25. 

 The finally adopted corrections on I. M.S. have been applied for all C.I.W. instruments. 



The outside west pier, W, heretofore used for intercomparison work, was rejected 

 for the present series as it was found to be constructed of magnetic material. Accord- 

 ingly two new outside stations designated as A and B were established and used in addi- 

 tion to the north pier, N, and the southeast pier, SE, of the absolute observatory, 

 occupied in previous comparisons. A is 50.51 feet and 48.53 feet from the northwest 

 and southwest corners, respectively, of the concrete base of the atmospheric-electric 

 laboratory, and 26.82 feet from the Observatory rain-gage. B is 50.32 feet from A 

 towards the steeple of Tuamua Church across the bay in true bearing south 95 46'. 6 

 west. The Observatory value for the azimuth of the steeple of Tuamua Church from 

 N was used, as in 1915, viz, south 96 lO'.l west. After finding that the west pier was 

 constructed of magnetic material, tests were also made of the piers in the absolute 

 observatory. These, however, were found to be non-magnetic. 



The observations were made as nearly simultaneously as possible. Simultaneous 

 observations were also obtained with C.I.W. magnetometer-inductor No. 24 mounted 



