48 



Anniversary Meeting. 



[Nov. 30, 



Society's present and future income. It may interest yon to know that 

 the contribution of ordinary Fellows in future to be elected, is but 

 little over that which was required of all Fellows from the very 

 commencement of the Society's existence till 1823, namely, Is. per 

 week, and that the last Fellows who paid that sum died in 1869. 



Looking back over the five years during which I have occupied this 

 chair, I recognise advances in scientific discovery and research at 

 home and abroad far greater than any previous semi- decade can 

 show. I do not here allude to such inventions as the Telephone, 

 Phonograph, and Microphone, wonderful as they are, and promising 

 immediate results of great importance to the community ; nor even to 

 those outcomes of high attainments, the Harmonic Analyser of 

 Sir W. Thomson, and the Bathometer and Gravitation Meter of 

 Siemens ; but to those discoveries and advances which appeal to 

 the seeker of knowledge for its own sake, whether as developing 

 principles, suggesting new fields of research, or awakening attention 

 to hitherto unseen or unrecognised, or unexplained phenomena of 

 nature, and of which the Radiometer and Otheoscope of Crookes are 

 conspicuous examples. 



In the foremost rank as regards the magnitude of the undertakings 

 and the combination of means to carry them out, nothing in the history 

 of physical science can compare with the Transit of Venus Expeditions. 

 To observe the Transit of Yenus various nations of Europe and the 

 United States competed as to the completeness of the Expeditions 

 they severally equipped. The value* of the solar parallax cannot be 

 ascertained until the results of all the Expeditions are taken into 

 account, when it will have an international claim to acceptance. But 

 advances in this direction will not have ended here, the very difficul- 

 ties attending the observation of the Transit of Yenus, having directed 

 attention to the method originally suggested by the Astronomer 

 Royal in 1857, of obtaining the solar parallax from the diurnal 

 parallax of Mars at its opposition. 



Mr. Gill by the skilful employment at Ascension Island of the 

 heliometer lent by Lord Lindsay, has greatly increased the accuracy 

 of the method by which the necessary star comparisons with Mars are 

 made, and there is every reason to believe that the results of his 

 observations which are now in course of reduction will be very satis- 

 factory. 



Within the last two years a remarkable addition has been made to 



* The Astronomer Royal informs me that Captain Tupman, who has taken the 

 principal share in the superintendence of the calculation, fixes provisionally on a 

 mean parallax of 8"'8455, coiTesponding to a distance of 92,400,000 British miles, but 

 that the observations -would be fairly satisfied by any parallax between 8 //- 82 and 

 8""88, which in distance produces a range of from 92,044,000 and 92,770,000 miles, 

 differing by 726,000 miles, a quantity almost equal to the sun's diameter. 



