Wellington Philosophical Society. 503 



It is satisfactory to find that the longitude which is at present used for 

 finding the local New Zealand time is within 'SI of a second of that which is 

 given by the observations now communicated by Captain Nares as the result 

 of the investigations of the officers of H.M.S. " Challenger." Thus, the chart 

 longitude at present used to find the local Wellington time, in accordance with 

 a decision arrived at by the Board appointed in 1870 (App. to Journ. 



H. M. SEC. 



H. of R., D— 27), is 11 39 11-53 



The longitude for the same, deduced from 

 the longitude now given by the "Challenger" 



H. M. SEC. 



from the Wellington Observatory, is ... ...11 39 07" 84 



Pipitea Point, E. ... + 2-88 11 39 10-72 



Difference ... ... ... ... ... -81 



It is true that the longitude, as determined by the absolute observations of 

 Chief Surveyors Jackson and Thomson (App. to Journ., 1871, G — 23), would 

 appear to be llh. 39m. 18 -19 sec, but this longitude has never been 

 accepted in the practical working of the Observatory, as it would involve the 

 serious consequences pointed out in the latter part of Captain Nares' memo- 

 randum ; and as it differs from all chronometric measurements, which, in the 

 opinion of the Astronomer Royal and Professor Ellery, are more reliable than 

 absolute determinations, owing to the defects in the lunar tables. 



As to Captain Nares' remarks relative to the method at present adopted of 

 giving the time-ball signals, I venture to differ from his conclusion on the 

 subject, as he appears to be under a misconception as to the method which is 

 in use. When a time-ball drops in any part of New Zealand, a ship's 

 chronometer, if set, as is usually the case, to Greenwich Mean Time, should 

 show 12h. 30 m., and any difference from this will be the error, fast or slow, 

 on Greenwich Mean Time. The local time at any port can at once be obtained 

 by applying the difference between the chart longitude for that place and 

 llh. 30m. E., or 172° 30' E. of Arc. This appears to be as simple a method, 

 both for rating and correcting chronometers, as can well be contrived, and is, 

 besides, in accordance with the practice adopted round the coasts of England 

 and Scotland, where Greenwich time, and not the time at place, is indicated 

 by the local time-balls. 



I cannot therefore concur in the suggestion that, in giving the time-signals 

 in different parts of the colony, local mean time at place should be adopted. 



As the correct longitude of Wellington Observatory, being the initial 

 longitude for New Zealand, will be required by the officers in charge of the 

 observation of the transit of Venus, I may state that the longitude, as 

 determined from the difference between Sydney and New Zealand, measured 

 by Captain Stokes — and corrected for the error since ascertained for the 



