DEPARTMENT OF TERRESTRIAL MAGNETISM. 237 



and those on expeditions up the Xingu and Trombetas Rivers, tributaries of 

 the Amazon, practically all the stations occupied have been those at which 

 observations had been previously made, either by observers of this Depart- 

 ment or of other organizations. In general, the reoccupations were suffi- 

 ciently exact, and the time interval since the last occupation of such duration 

 that satisfactory data for determining secular variation were secured. 



To extend our knowledge of the diurnal variation in the three magnetic 

 elements beyond that obtained by the existing and widely scattered magnetic 

 observatories, the special diurnal-variation program was developed further 

 to include such work for inclination and horizontal intensity as well as 

 declination at field stations. At selected stations from 500 to 800 miles 

 apart and designated as Class I stations, observations were made to deter- 

 mine the diurnal variation during the daylight hours in horizontal intensity 

 by means of deflection observations at one distance, repeated at short inter- 

 vals; the method followed gives also the variation in declination as well. 

 On a succeeding day repeated observations with the earth inductor are made 

 from which the diurnal changes in inclination are derived. At Class II 

 stations the usual program of observations is repeated on successive days, the 

 observer endeavoring to so select the time of observations that a value of 

 each element may be obtained near the time of its daily maximum and its 

 daily minimum. 



Field operations. — Three observers have continued in the field throughout 

 the entire year and a fourth since the end of December. With the exception 

 of two months spent in the Pacific Islands, Mr. Coleman continued in Aus- 

 tralia; Mr. Green, after work along the north coast of Venezuela, proceeded 

 southward through eastern Brazil to Argentina, and thence overland through 

 Bolivia to Peru; Mr. Howard, who joined Mr. Green in January and accom- 

 panied him as far as the mouth of the Amazon, worked thence along that 

 river and its tributaries; Mr. Love, after an expedition into Colombia, South 

 America, returned to Guatemala and other Central American states. Mr. 

 Goddard joined the MacMillan North Greenland expedition on June 9, 

 with which he continued throughout the year. (See also cooperative work 

 with the Liberian Boundary Survey, p. 240.) 



A brief synopsis of the year's work on these various expeditions follows : 



1. Australasia. — After completing his work in connection with the eclipse 

 of September 21, 1922, Observer D. G. Coleman reoccupied stations in Queens- 

 land, Australia, along the railways leading inland from Brisbane and Rock- 

 hampton. After spending the months of November and December in the 

 Pacific islands, he took up work in Tasmania, arriving on January 19; after 

 reoccupying stations at Latrobe, Longford, Hobart, Sorell, and Southport, 

 he returned on February 12 to Melbourne, New South Wales. From Mel- 

 bourne he proceeded to South Australia, making comparison of his instru- 

 ments with the standards of the Adelaide Observatory at Mount Lofty in 

 the latter part of February. After reoccupying four additional stations in 

 South Australia, he proceeded to Watheroo, where he compared his instru- 

 ments with those of the Watheroo Observatory during April 5 to 10. On his 

 return from Watheroo, he met Mr. Kennedy, of the South Australia Observa- 

 tory, at Port Augusta, where comparisons were again made with the instru- 

 ments of the Adelaide Observatory, He then proceeded through South 

 Australia and New South Wales, reoccupying stations including Oodnadatta 

 and Burke, to Red Hill, near Sydney. His next work was in northern Queens- 

 land and the York Peninsula; he arrived at Thursday Island September 5, 



