MAGNETIC OBSERVATIONS AT FALMOUTH OBSERVATORY. 75 



of England, the Committee think it most important that the Falmouth 

 observations should be maintained, and they ask therefore for reappoint- 

 men, with a grant of 501. 



By an arrangement recently made between the Royal Society, the 

 Meteorological Office, and the Treasury, the responsibility for the 

 magnetic and meteorological work at Kew and Eskdalemuir now rests 

 with the Meteorological Office. The Committee therefore recommend 

 that the name of Dr. Shaw be added to the Committee, and that he be 

 the Secretary of the Committee. 



Geodetic Arc in Africa. — Report of the Committee, consisting of Sir 

 George Darwin {Chairman), Sir David Gill {Secretary), Colonel 

 C. F. Close, and Sir George Goldie, appointed to carry out a 

 further portion of the Geodetic Arc of Meridian North of Lake 

 Tanganyika. 



The grant (100L) has been paid to H.M. Treasury. The field work for 

 which the grant was made has been completed, and the computations 

 are finished, excepting the final reduction of the observations of latitude. 



Report by Captain E. M. Jack, R.E. 



The measurement of a portion of the 30th meridian arc, to the 

 cost of which the British Association made a contribution of 1002., was 

 carried out in the Uganda Protectorate in 1908-09, the personnel 

 employed being as follows : — 



British Section. — Observers : Captain E. M. Jack, B.E., and 

 Mr. G. T. McCaw, M.A. Assistants: Lance-Corporals Jones, R.E., 

 and Page, R.E. Medical Officer: Mr. C. L. Chevallier. 



Belgian Section. — Astronomer: Dr. Marcel Dehalu. Assistant: 

 Captain G. Wangermee. 



The instruments used were two 10-inch Repsold theodolites, lent 

 by the Intercolonial Council of the Transvaal and Orange River Colony; 

 and a 3-inch zenith telescope, lent by the War Office. 



Observations of terrestrial angles were made to heliostats by day and 

 to acetylene lamps by night. Angles were measured on eight settings 

 of the circle, two measures C.R. and C.L. being taken on each setting. 

 Vertical angles were measured in the afternoon. 



Latitudes were observed at fourteen out of the sixteen main stations. 

 The Talcott method was employed, and usually 15 to 20 pairs of stars 

 observed at a station. 



Azimuths were observed at three stations, at each end and in the 

 middle of the chain. 



A base 16A- kilometres (10J miles) long was measured. Six invar 

 wires were used, three being kept for reference purposes only, and three 

 for actual measurement. No standard bar was carried. The base was 

 divided into sections of about one kilometre, and each section was 

 measured twice, each measurement being made with two wires. A 

 third measure of a section was made in the few cases when there 

 appeared to be an abnormal discrepancy between the first and second. 



