552 PROCEEDINGS OF SECTION E^ 



In 1873 a member of the Survey Department exchanged time 

 signals with the Observatory from Ahce Springs Telegraph Station. 

 This was done again by another oflicer in December, 1880. The mean 

 of the two sets was 18' 51", which, adapted to the present published 

 longitude of Adelaide, gives 133"^ 52' 20" for AUce Springs. 



In 1880 one of the same officers exchanged time signals with the 

 Observatory from Tennant's Creek Telegraph Station, the difference 

 of time being 17min. 28secs., from which 134° 13' 04"-5 has been adopted 

 for the present longitude of that station, subject to an uncertainty 

 of 300yds. 



In 1880, at the time of the Herbert River pastoral blocks being 

 offered for sale, ]\lr. C. Winnecke fixed the longitude of Lake Nash 

 by occultation of Jupiter's satellites (2), and of a stone pile at the junc- 

 tion of the Herbert and James Rivers by observations consisting of 

 moon culminating stars and moon occulting stars (3). The circum- 

 stances, however, were not favorable, and the longitude so obtained 

 was not adopted. Subsequently, by chainage of pastoral surveys 

 connecting the junction pile and the overland telegraph line, the longi- 

 tude of the line where it crosses the Fergusson River ^h as been found 

 to be 133= 38' 46". 



LINE TO GULF OF CARPENTARIA. 



The demarcation of the 138th meridian of east longitude, dividing 

 Queensland from the Northern Territory, was carried out during 

 1883-1886 by Messrs. Poeppel and J. Carruthers, assisted by Mr. L. A. 

 Wells, Government Surveyors of this State. The point of commence- 

 ment was ascertained by chainage from the eastern boundary line in 

 1880-81, checked by triangulation connected with the newly deter- 

 mined longitude of Adelaide Observatory. The south-west corner of 

 Queensland is, therefore, correctly fixed, and this is the more satis- 

 factory, as the line surveyed thence to the Gulf of Carpentaria proved 

 to be a costly undertaking, and is the longest surveyed straight line 

 in the world — 650 miles 5,700 links. 



MOUNT GAMBIER. 



During recent years the longitude of Mount Gambier Trigono- 

 metrical Station has been calculated from Adelaide, partly by triangu- 

 lation and partly by chainage of hundred boundary lines compared 



(2) Occultation of Jiipiter's Satellites.— The Greenwich mean times of disappear- 

 ance and reappearance of Jupiter's satellites are given in the Nautical Almanac, 

 and from observation at any other place of the local time at which these phenomena 

 occur, the difference of time, and, therefore, the difference of longitude, is found. 



(3) Moon Occulting and Moon Culminating Stars. — By the term occulting 

 is meant the observations necessary to compute the exact right ascension of the 

 moon at the moment that a star in its path is hidden by the bright edge of the- 

 moon. From the difference between the right ascension so found and that given 

 in the Nautical Almanac for Greenwich mean time, as if viewed from the centre 

 of the earth, the longitude of the observer is deduced. 



Culmination is the term employed when the moon's right ascension is found 

 by observation of moon and stars passing the meridian nearly at the same time. 



