56 PROCEEDINGS OF SECTION A. 



If we connected, Mt. Stromlo both with Southport and Port Darwin 

 as well as with the existing observatories we would obtain a series of 

 arcs by which we could form an uniform system of difierential longi- 

 tudes referred to the meridian of Mt. Stromlo as their origin, but the 

 absolute value of the Australian longitudes including that of their 

 initial meridian would still remain afiected by the same amount of un- 

 certainty as at present. 



In all these cases, to carry out even a single connexion between 

 Mt. Stromlo and any one of the State Observatories with due efficiency, 

 the same equipment as that described in these pages for the complete 

 scheme would have to be provided. 



These reasons lead to the conclusion that the proposed measurement 

 of the longitudinal arcs between Southport (Queensland) and Madras, 

 through Port Darwin and Singapore, including in the general scheme 

 Mt. Stromlo and other Australian Stations such as the Observatories 

 of Brisbane and Perth, which do not appear on the direct route, gives 

 us the opportunity of discharging a scientific obligation, of rendering 

 a valuable service for an object in which other countries are directly 

 interested, and of establishing an initial meridian for the Commonwealth 

 whose position will be known with a precision adequate to its scope. 



On these grounds it seems justifiable to strongly recommend the 

 authorities to provide means for carrying out the proposed work. 



It is well known that to find the difference of longitude between 

 two places, two operations are required ; first, a determination of local 

 time, and, second, a comparison of the two distant clocks at a definite 

 absolute instant. 



For more than 60 years these clock comparisons have been obtained 

 wherever possible, by exchanging clock beats with telegraphic apparatus 

 along the telegraph lines and submarine cables. • 



More recently Wireless Stations have been utilized for transmitting 

 clock signals by Hertzian waves in longitude determinations of high 

 accuracy. 



The first experiments were made in 1904 by Prof. Albrecht and 

 Prof. Wanach (*), who found that the accuracy obtainable by the 

 employment of wireless apparatus in transmitting clock signals was of, 

 the same order as that given by the ordinary telegraphic instruments. 

 In 1906 the same astronomers proceeded to employ both the wire- 

 less and the usual telegraphic method in measuring the difference of 

 longitude between Potsdam and Brocken. (f) 



The transmitting wireless station was Narren, at a distance of about 

 20 miles from Potsdam and 114 nailes from Brocken. The signals were 

 sent by the oscillations of a pendulum at intervals of 2 -4 sees. These 

 were recorded on the chronographs at the two terminal stations. 



* Astro no mische Xachrichten N° 3982. 



t Veroflentlichung des Konigl Preuszischen Gsodatischen Instituts. Neue Folge Nr. 31. 

 Prof. Dr. Th. Albrecht. Bestimmung der Langendiflerenz Potsdam-Brocken im Jahre, 1906. 



