PROCEEDINGS OF SECTION E. 



555 



Annexed will be found a schedule of geographical positions which 

 may be accepted as correct within two or three seconds of arc. 



A study of the foregoing details brings to the surface the fact 

 that astronomically observed intervals of both latitude and longitude 

 are longer than their measured values. This is precisely what Sir 

 David Gill has found to be the case in the triangulation of South Africa, 

 and indicates that either the dimensions of the earth used in calcula- 

 tion are not in strict conformity with this part of the globe ; or that 

 the unit of measure adopted here is slightly too long (say, one-fifteenth 

 of an inch per chain). 



This paper shows conclusively that longitude obtained by obser- 

 vation of lunars (occultations, and of moon culminating stars) are 

 useless as absolute determinations for any other than nautical or 

 exploratory purposes ; whilst telegraphic time signals are so accurate 

 that the distance between Adelaide and Melbourne observatories 

 obtained thereby, in conjunction with latitude, agrees to within a few 

 yards with the distance actually measured. 



SCHEDULE OF GEOGRAPHICAL POSITIONS. 



The official figures used herein have been quoted by permission of the Surveyor- 

 General. 



