Klotz. — Transpacific Longitudes. 61 



in that year the question arose, why the known error in longi- 

 tude of 2' 30 " was not corrected on the Indian maps and charts. 

 This gave rise to a discussion in India, and the whole longitude 

 work was reviewed, with the result that a determination de novo 

 Avas decided upon, carrying the work directly from Greenwich 

 via Potsdam, Teheran, Bushire, and Karachi, where connection 

 was made with the three arcs of the great trigonometrical sur- 

 vey between Karachi and Madras. This work was carried out 

 by Captain (now Major) S. G. Burrard, R.E., and Lieutenant 

 Lenox Conyngham, R.E., in 1894-6. The resulting longitude 

 of Madras was 5 h. 20 m. 59-137 s. + 0-022 s. 



In 1903 a redetermination of Greenwich-Potsdam was carried 

 out by Professor Dr. Albrecht and Mr. Wanach. Stations were 

 exchanged and observations made with a Repsold registering- 

 micrometer. The exchange of stations was made to test the 

 elimination of personal equation by means of the registering- 

 micrometer, and the result was highly satisfactory, the weighted 

 mean of the one result agi'eeing with the weighted mean of the 

 other to the third place of decimal of a second of time. It may 

 be stated here that the introduction of the registering-micro- 

 meter in longitude-work marks a distinct epoch in that class of 

 work, not only in assuring greater accuracy in the results, but 

 also in very materially reducing the cost of longitude-work of 

 the first order by saving of time and money in doing away with 

 the necessity of exchange of stations. Since the completion of 

 the transpacific longitude-work, the two Cooke transits used in 

 that campaign have been provided with the registering- micro- 

 meter made by Saegnmeller, of Washington, and the longitude 

 work of 1905 was carried out with that attachment. 



From the 1903 determination bv Albrecht we have for the 

 longitude of Potsdam h. 52 m. 16-051 s. ± 0-003 s. This value 

 is 0-098 s. greater than that of Burrard obtained in the series 

 of 1894-6 referred to above. 



In the reduction (1885) of the Australian longitudes, the 

 longitude of Madras was accepted as 5 h. 20 m. 59-42 s., and the 

 derived value of Sydney was 10 h. 4 m. 49-54 s. 



In making the comparison between the longitude of Sydney 

 as brought from Greenwich eastward with that brought west- 

 ward, the best and most recent available data are utilised for the 

 longitude of Madras. 



■ Taking, then, Albrecht's value for the arc Greenwich-Pots- 

 dam, and the values of Burrard for the arcs Potsdam-Madras, we 

 obtain for the longitude of Madras 5 h. 20 m. 59-235 s. + 0-021 s. 



As there have been no new determinations of the various 

 arcs from Madras to Sydney, the values given in the report of 

 May, 1885, by Ellery, Todd, and Russell, on Australian longi- 

 tude, are used. Adding the latter to the above-accepted value, 



