76 W. G. WOOLNOUGH. 



The triclinic model consists simply of a spherical cork, 

 on opposite sides of which, supported by large pins are two 

 triangular cards in the positions necessitated by the centre 

 of symmetry, which is the sole element of symmetry of the 

 group. 



Provisional DETERMINATION of ASTRONOMICAL 

 REFRACTION, from Observations made with the 

 Meridian Circle Instrument of the Sydney 

 Observatory. 



By C. J. Merfield, f.r.a.s., 

 Mitglieder der Astronomischen Geseilschaft. 



[Read before the Royal Society of N. S. Wales, November 1, 1905.~] 



CONTENTS. 



1. Introduction. 



2. Instrument. 



3. The Observing Room. 



4. Meteorology. 



5. Method of determining the Refractions. 



6. Observations. 



7. Errors of graduation of the Circle. 



8. Reductions of the Observations. 



9. Final Results. 



10. The Constant of Refraction. 



11. Conclusion. 



1. Introduction. 

 For some years past the meridian circle instrument of 

 the Sydney Observatory has been in constant use for 

 observing the transits and zenith distances of certain stars. 

 The working lists have been prepared for the purpose of 

 providing data for deducing the constants of reduction 

 for the photographic plates, taken with the astrographic 

 telescope. Eventually the positions of the stars, observed 



