Eichakdson. — On the Survey System. 497 



expansion of which have been ascertained, and with the 

 work carried on under the best atmospheric conditions. 



The two base-lines of the Spitzbergen arc were measured 

 by a method introduced by Professor E. Jaderin, of Stock- 

 holm, in 1885. It differs, however, but little from that em- 

 ployed by the United States Geodetical Survey, except in 

 respect of the length cf band or wires used (Jaderin, 

 25 metres ; United States Coast and Geodetical Survey, 

 300 ft.), and both processes give almost identical results, or 

 about 1 in 1,000,000, or a probable error of, say, 1 in. in 

 sixteen miles. This accuracy constitutes a forcible protest 

 against our present chain - standard differences, with their 

 mean probable error of xVo" 1 - P er chain, or 12 in. per mile. 



The modern bases used for primary triangulation average 

 about six miles, and do not exceed four hundred miles apart ; 

 for secondary, three miles base, one iundred miles apart; and, 

 for tertiary (commonly called minor triangulation), one mile 

 and a half base, and thirty miles apart. The cost of measur- 

 ing these bases varies from, probably, not less than £400 per 

 mile for ^yin. per mile error to £30 per mile for £in. per mile 

 probable error. 



These detail matters, however interesting, are perhaps out 

 of place when dealing with the main question ; so also the 

 magnetic observations now undertaken by the New Zealand 

 Survey Department ; and in the same category come tidal 

 measurements, which are necessary to geodetic accuracy, and 

 here as yet are inadequate. Wellington, Westport, and Grey- 

 mouth represent the South at present, while it requires tide- 

 gauges at the Bluff and x\karoa to complete the surround and 

 establish the necessary reference to " mean sea-level " for the 

 South Island ; and the North Island would require similar 

 attention. 



The time has now arrived when the perfecting of our sur- 

 vey system has become necessary, and as we can, at small 

 additional cost, largely advance the interests of science while 

 doing so, we should endeavour to compass the two aims in 

 one operation. Looking to what has been effected, to what is 

 now being undertaken, and to what is in contemplation, it 

 seems scarcely open to question that long before the middle 

 of this century is reached all the pathways in the Southern 

 Hemisphere available to geodesy will have been trodden, that 

 the New Zealand arc will probably by then have been merged 

 in a great Australasian arc extending from Cape York (11° S.) 

 to Stewart Island (47° S.), and that the Commonwealth will 

 also have contributed an arc of parallel from Perth to Syd- 

 ney. The question now is, Is New Zealand, which takes 

 "honours" in most subjects, prepared to seize the oppor- 

 tunity and step into the front rank of science. 

 32 



