24 PROCEEDINGS OF SECTION A. 



3.— ON THE ALMUCANTAR METHOD OF OBSERVING STAR 



POSITIONS. 



By 0. F. Dodwell, B.A., F.R.A.S., Government Astronomer, South 



Australia. 



(Abstract.) 



In this paper the author describes the very accurate method of 

 making astronomical observations which was introduced by Professor 

 S. C. Chandler, of Harvard Observatory, U.S.A., about 30 years ago. 

 It consists in observing the passages of stars across an imaginary 

 horizontal line in the sky passing through the celestial pole. Chandler 

 used a special instrument, but the method was adapted for use with a 

 surveyor's theodolite in 1902 by Mr. W. E. Cooke, now Government 

 Astronomer of New South Wales. This method was used by the 

 author in February, 1911, for the determination of longitude near the 

 boundary obelisk, erected in 1869, by Sir Charles Todd on behalf of 

 South Australia, and Mr. G. R. Smalley, on behalf of New South Wales, 

 to mark the 141st meridian, a few miles north of the spot where it 

 crosses the River Murray, near the telegraph line to Sydney, via 

 Wentworth. Some of the details of the recent determination were 

 given, and the opinion was expressed that the system of observation 

 employed on the occasion, if used with astronomical instruments of 

 the first class, might be profitably adopted int he operations of funda- 

 mental astronomical work. 



4. DETERMINATION OF THE ERRORS OF THE R£SEAUX, 

 MELBOURNE No. 6 AND MELBOURNE No. 23. 



J. M. Baldwin, M.A., D.Sc, Melbourne Observatory. 

 (Abstract.) 

 In this paper the methods adopted by the author for the deter- 

 mination of the errors of the reseaux iised at the Melbourne Observatory 

 in connexion with the photographic catalogue of the heavens are 

 described. Each reseau should consist of two sets of equidistant 

 parallel straight lines at right angles to one another, and hence it has 

 been necessary to investigate- - 



(1) the equidistance of the lines ; 



(2) the parallelism of tjie lines ; 



(3) the rectangularity of the sets of lines ; 



(4) the rectilinearity of the lines. 



The investigation has extended to each point of intersection of 

 the lines, and the resulting errors have been combined and tabulated. 

 The limiting corrections are — 



~ 'OOS mm. and -i- "006 mm. for reseau Melbourne No. 6. 

 — •Oil mm. and + '012 mm. for reseau Melbourne No. 23. 



