Instrumental Equipment of Parties 7 



number 2025. This instrument was used only for a few stations in 1906 on islands 

 in the Pacific Ocean; its loan was obtained through the courtesy of the authorities 

 in charge of the Samoan Observatory. It is somewhat complex and intricate 

 in construction. In the determination of the horizontal intensity, it was used as 

 a relative instrument, the results being computed only from deflection observations; 

 the relative constants and their changes with time were determined from obser- 

 vations at the Samoan Observatory before and after the field work, at Suva, Fiji, 

 from intercomparisons with the Galilee party, and at the Christchurch Magnetic 

 Observatory. As the deflection distances were not measured, no determinations 

 of the distribution coefficients were made. The diameter of the horizontal circle 

 is 12 cm., reading arrangements by microscopes being such that the least count is 

 0.2 minute; the diameter of the vertical circle is 10 cm. and least reading 1 minute. 

 A complete description is given by Prof. K. Haussmann in the January number 

 (1906) of the Zeitsclmfi fur Instrumentenkunde. 



In addition to the above enumerated magnetometers the Department has also 

 at a few stations used magnetometer No. 8 of the United States Coast and Geodetic 

 Survey. This instrument is one of the earlier styles used by the Survey, with 

 cylindrical magnets, as manufactured by Jones of London, and is in a general way 

 similar to the magnetometer of type 2, design (a), as described above. 



Magnetometer No. 7041, used at Battle Harbor, Labrador, in 1905, was of the 

 Bamberg type. A complete description of this instrument will be found in the 

 journal Terrestrial Magnetism, v. 8. (130-143). 



In the Table 1, on page 8, C.I.W. stands for Carnegie Institution of Wash- 

 ington (Department of Terrestrial Magnetism) ; di and dz, the inside and outside 

 diameters, respectively, of the magnet referred to; Ph. Br. for phosphor-bronze 

 suspension. The quantities refer throughout to C. G. S. units and the value of 

 q is given for 1 C. 



Dip Circles. 



The dip circles used have been of four patterns: (a) the regular Kew land 

 pattern as made with slight variations by Dover and by Casella; (b) the Lloyd- 

 Creak ship pattern as originally designed by Captain Ettrick W. Creak and made 

 by Dover with some modifications introduced by the Coast and Geodetic Survey 

 and by the Department according to L. A. Bauer's specifications; (c) the Brunner 

 pattern of the Magnetic Survey of France as made by Chasselon, and {d) the 

 pattern as designed by Eschenhagen and made by Tesdorpf as a part of his universal 

 magnetometer. For the greater part of the work circles of the first and second 

 patterns, (c) and (b), were used. 



All of the Kew pattern instruments' used are essentially similar except in minor 

 mechanical details and in the matter of the provision of horizontal or vertical agate 

 supports and needle lifters, the former for observations in regions of high magnetic 



' For more detailed descriptions see Stewart & Gee's Practical Physics, and the article by William Watson on 

 "Inclinometer" in EnoyclopcBdia Britannica, 11th Edition, v. 14. (354-355.) 



