440 Transactions. — Chemistry and Physics. 



It is interesting to note some of the alterations which have 

 been made in the recorded longitude of Sydney Observatory 

 during the past thirty years, and to compare them with the 

 smaller corrections which have been necessary in the assumed 

 longitude of Melbourne. From old volumes of the " Nautical 

 Almanac '•'* and from other sources we find that since 1874 

 the following values have been used for these two observa- 

 tories : — 



Sydney. Melbourne. 



H. M. S. H. M. S. 



E. 10 4 53-371 E. 9 39 54-8 



9 39 53-8 



9 39 54-15| 



The first reliable determination of the difference of longi- 

 tude between Sydney and Wellington was effected in the 

 years 1852 and 1854 by H.M. ships " Acheron " and " Pan- 

 dora," under Captain J. L. Stokes and Commanders G. H. 

 Kichards and B. Drury, by the transport of chronometers 

 from Sydney to Wellington during the course of the complete 

 survey made by those vessels of the New Zealand coast. 

 The place selected in Wellington was a spot near Pipitea 

 Point, on what is now the railway-line (it used to be marked 

 on the old charts as "Observation Spot"). When the Ob- 

 servatory was afterwards built its difference of longitude 

 from that position (viz., 2*88 s.§) was easily ascertained by 

 triangulation. The result thus obtained was subsequently 

 confirmed by telegraphic determinations. In 1876 Mr. H. C. 

 Kussell at Sydney Observatory and Archdeacon Stock at 

 Wellington Observatory exchanged a series of cable time- 

 signals which gave a mean result accordant with that of 

 Captain Stokes to within about half a second of time, show- 

 ing how admirably that officer had done his work;|| and 

 again, in 1883, Mr. Russell at Sydney Observatory and 



*See "Nautical Almanac" for 1883, 1889, 1894, 1896, 1897, 1898, 

 and 1903. 



f Absolute determination. 

 \ Present value. 



§ The transit pier of the Observatory is 5015-6 links west of Observa- 

 tion Spot at Pipitea, equal to 2-88 s. in time. 



|| See Trans. N.Z. Inst., vol. ix., 1876, p. 217 : " On the Longitude 

 of Wellington Observatory," by Yen. Archdeacon Stock, B.A. 





