92 



Anniversary Meeting. 



[Nov. 30, 



and Superintendent of Telegraphs at Adelaide, would be prepared to 

 take in it under the auspices of his Government. The eastern boundary 

 of the colony having been defined by Imperial Act as the 141st 

 meridian, a wish has been expressed officially for the accurate con- 

 nexion of Adelaide with Greenwich, independently of the Transit of 

 Venus. 



The Astronomer Royal has explained in detail the preparations 

 which he considers necessary, so far at least as this country is con- 

 cerned, for the effective observation of the transit, and he has 

 introduced several alterations in the plan which he had \ formerly 

 suggested. The experience of the transit of 1874 points to the de- 

 sirability of sacrificing something in the magnitude of the parallax- 

 factor for the sake of securing a higher elevation of the sun ; thus, 

 for retarded ingress, Sir George Airy had at first proposed to refer 

 principally to the coasts of the Canadian Dominion and the United 

 States of North America, where the sun's elevation is from 15° to 18°; 

 he now proposes to substitute for this the whole chain of West India 

 Islands, from the eastern extremity of Cuba to Barbadoes, or stations 

 on the neighbouring continent of Central America. Bermuda is also 

 included as a favourable point for observation. Most, if not all, of 

 the longitudes required have been determined with great precision by 

 the Hydrographic Department of the United States. For ingress 

 accelerated, Sir George Airy relies entirely upon stations in the Cape 

 Colony. For the accelerated egress, all the stations suggested for 

 ingress retarded will be available. For egress retarded, although 

 the fixed Observatories at Melbourne and Sydney will contribute to 

 the observation of the phenomenon, they will have the sun at a some- 

 what low elevation (10 — 14°) ; it is therefore proposed to rely mainly 

 upon New Zealand, with which we are in telegraphic communication 

 via Sydney. Considerable correspondence has taken place on the 

 subject of Australian longitude, and it is expected that the necessary 

 steps to effect the connexion of one of the Observatories, probably 

 Adelaide, with Madras, will be taken early in the ensuing year. 



Sir G. B. Airy has completed the laborious calculations in his 

 Numerical Lunar Theory, from which the corrections to the co- 

 efficients of Delaunay's Lunar Theory are to be deduced ; and in con- 

 nexion with this work, he has made an investigation of the value of 

 the Moon's Secular Acceleration, for which he finally obtained the 

 value 5' /, 477, thus confirming the results obtained by Professor 

 Adams, and subsequently by Mr. Delaunay. On this important 

 question, Professor Adams has also published an investigation. 

 (" Monthly Notices," vol. xl, Nos. 411 and 472.) 



A new determination of the Physical Libration of the Moon from a 

 large number of lunar photographs taken with the De La Hue reflec- 

 tor at the Oxford University Observatory has been recently made by 



