DEPARTMENT OF TERRESTRIAL MAGNETISM. 199 



The manifestations of solar activity, with their resulting emanations and 

 radiations, seem not to be the direct but the indirect cause of the earth's 

 magnetic storms. Their effect appears to be more in the nature of a releasing 

 or "trigger" action, setting in operation electric energy already in existence 

 in the upper regions of the atmosphere ; terrestrial sources in reality, how- 

 ever, supply the energy required for the magnetic storm. To account then 

 for the well-established, general relationship between magnetic disturbances 

 and the sun-spot period, we must suppose that the radiations which alter the 

 conductivity of the atmosphere vary in their amount and intensity in accord- 

 ance with the periodicity of the solar phenomena. 



In conclusion, it is but due to the members of the departmental staff, in 

 general, and specifically to the commander of the Carnegie, Mr. W. J. Peters, 

 and to the magnetician in charge of office, Mr. J. A. Fleming, that acknowl- 

 edgment is made hereby of the effective and cordial assistance rendered in 

 the successful execution of the various operations of the Department. 



DETAILS OF MAGNETIC WORK DURING THE YEAR, NOVEMBER 1, 1909, 



TO OCTOBER 31, 1910. 



EAND WORK. 



Africa. — The itinerary for work, as outlined in last year's report, entrusted 

 to Dr. J. C. Beattie, Research Associate, assisted by Prof. J. T. Morrison, 

 Magnetic Observer, has now been completed. An inspection of the work 

 shown for Africa on the accompanying map (plate 5) will serve to give 

 some idea of the numerous data obtained in a laborious campaign well car- 

 ried out. The distribution of stations occupied during October 1908 to Jan- 

 uary 1910 is as follows: Jointly by both observers, 6 in Belgian Kongo, I 

 in Cape Colony, 1 in Egypt, 1 in England, and 39 in Rhodesia — in all 48; 

 by Dr. Beattie, 36 in Cape Colony, 45 in German Southwest Africa, 60 in 

 German East Africa, 3 in Rhodesia, and 33 in the Uganda Protectorate — in 

 all 177; by Professor Morrison, 35 in British Central Africa, 28 in British 

 East Africa, 4 in Cape Colony, 10 in German East Africa, 24 in German 

 Southwest Africa, 6 in Portuguese East Africa, 15 in Rhodesia, and 1 in 

 Zanzibar — in all 123. The total number of stations is 348. Such a large num- 

 ber of stations was made possible by the plan adopted of taking observations 

 at each camping-place. The results will accordingly furnish also knowledge 

 regarding locally disturbed regions along the line of work. In addition to 

 the results obtained on this expedition, Dr. Beattie has placed in the hands 

 of the Department for reduction observations made by Professor Morrison 

 and himself at 15 stations during June and July 1908, in Cape Colony, Natal, 

 and Transvaal; also observations by himself during January to February 

 1907 at 18 stations in Cape Colony. Intercomparisons of standards were 

 made for the instruments used in this work at the magnetic observatories at 

 Helwan and Kew. 



China. — No field work was done in China during the year. However, the 

 necessary preparations have been made for extended campaigns in following 



