50G Proceedings. 



will, no doubt, present itself of verifying and correcting this as soon as the 

 telegraphic cable is laid between New South Wales and New Zealand. 



It is perhaps as well for us to point out in this paper that the present 

 method of dropping the ball at "Wellington, which method is, we understand, 

 adopted over the whole of the New Zealand islands, is liable to lead to grave 

 error. 



It must be evident that in order that a time signal should be of use for 

 purposes of navigation, that signal should be given on a principle which 

 admits of its being readily applied to the charts on which the seaman plots 

 the position of his vessel. These charts are all graduated on a certain system, 

 and on an assumed longitude of a selected position on each sheet, which 

 longitude is the subject of most careful attention at the Hydrographic Office, 

 and every longitude on^ or adjacent to, one well-determined position is 

 made to coincide with that position. Thus, every longitude on the published 

 chart of New Zealand is relatively correct with the given longitude of 

 Wellington. Now, the longitude of Pipitea Point on the chart is 1 74° 47' 53'' E., 

 while the ball at the Custom House has been dropped at an assumed time 

 of llh. 30m. from Greenwich, and this assumed time has been taken as being 

 9m. 15-75sec. west of the Wellington Observatory, or 9m. 18'63sec. from 

 Pipitea Point; therefore the ball was dropped as if Pipitea Point was in 

 longitude 174° 49' 39" E., or 1| miles east of the position given on the chart. 

 A ship, therefore, rating her chronometers by the ball at Wellington would 

 always be IJ miles west of the position plotted on the chart, and this might 

 be of serious moment. 



This difference, no doubt, has been caused by the desire of the colony to 

 adopt one mean time for the whole of the islands, an object the advantages of 

 which few people will dispute, and in doing which an error of a minute of time 

 in the absolute longitude assumed as the mean is of no moment. Very 

 different, however, may be the results when that empirical time is used as a 

 standard for seamen. Then every second becomes of consequence, and it is 

 necessary to be most careful that errors are not allowed to creep in. Probably 

 the only way to avoid this is to give a time signal at a certain specified 

 moment (say noon or 1 p.m.) mean time at j^^ace, which time can always be 

 ascertained correctly, leaving the seaman to apply the difference of time, as 

 denoted on his chart, between the place he is at and the meridian of Green- 

 wich. By this means he will always be certain that the astronomical position 

 of his vessel ascertained by him at sea is relatively correct with the adjacent 

 coast, both being laid off on the same chart. 



G. S. Nares, Captain 11. N. 



Captain Edwin thought that the time-balls should droji to local time, as 



