Wellington Philosophical Society. 505 



Taking the mean of these two results :. n. m. sec. 



Captain Stokes' meridian distance ... ... ... 1 34 18-16 



"Challenger's" ditto ... ^ 1 34 22-07 



2)40-23 



Mean ... ... 1 34 20-11 



The meridian distance between the Observatory at Sydney and Pipitea 

 Point will be Ih. 34m. 20-11 sec, and this is probably within half a mile of 

 the truth. It is, however, possible that, in taking the arithmetic mean of 

 these two meridian distances, we are giving our own too great a value, as, 

 owing to bad weather and the delay consequent on sounding for the telegraphic 

 cable from Sydney to New Zealand, twenty-one days elapsed between our 

 observations at Sydney and Wellington. 



If Captain Stokes ran his distance directly from Sydney to Wellington, as 

 he probably did, he would certainly have obtained observations at the two 

 places with a less interval of time, and his distance would therefore be of 

 much more value than ours. In the absence of precise information as to how 

 his distance was obtained, we have assumed for the present the two results to 

 be of equal value. The Observatory at Wellington is said to be 2 -88 sec. 

 west of Pipitea Point, the meridian distance therefore between the Observa- 

 tories at Sydney and Wellington will be Ih. 34m. 17-23sec. 



The next point to determine is the absolute longitude of the Observatory 

 at Sydney. That longitude was determined by Mr. Scott by absolute observa- 

 tions, and he made it lOh. 4m. 47*32 sec. E. of Greenwich. Lately 

 telegraphic time signals have been exchanged between the Observatories of 

 Melbourne and Sydney, and the meridian distance found to be 24m. 55-81 sec. 

 The longitude of the Melbourne Observatory, as determined by Mr. Ellery, is 

 9h. 39 m. 5 4 -8 sec. E. of Greenwich. By absolute determination, therefore, the 

 meridian distance between the two Observatories is 24m. 5 2 -5 2 sec, or 3 -2 9 sec. 

 difierent from the result obtained by telegraph, which result is necessarily 

 correct. It is therefore evident that either one or both of the determinations 

 for absolute longitude must be in error, and this error is most probably in the 

 Sydney determination, as better instruments were used at Melbourne. 

 Assuming, then, for the present that the longitude of the Melbourne Observa- 

 tory is correct. 



The longitude of Melbourne Observatory is 



Sydney Observatory east of Melbourne... 



Wellington Observatory east of Sydney Observatory ... 



Longitude of the Wellington Observatory ... ... 11 39 07-84 E. 



The longitude of the Observatory at Wellington may therefore, for the 

 present, be considered as llh. 39 m. 7- 84 sec. E. of Greenwich, Opportunity 



q2 



H. 



9 



M. 



39 



SEC. 



54-80 E. 





24 



55-81 E. 



1 



34 



17-23 E. 



