for the year 1875. xxxiii 



demonstrating the optical and structural peculiarities of 

 that instrument. 



On June the 14th, Mr. Alfred M. Smith read a paper on 

 " The Phenomena of Approach and Recession exhibited by 

 Bodies under the Influence of Radiant Energy," and 

 Mr. Harrison explained a form of universal equatorial, as 

 well as an instrument for assisting observations of the 

 planet Mars. 



I may now explain, for the elucidation of what follows, 

 that the laws of the Society provide for the formation of 

 eight sections, each devoted to specified departments of 

 scientific inquiry. In accordance with this provision, at a 

 meeting of members of the Royal Society, summoned by 

 the President, and held on the 21st of October 1873, it was 

 resolved to form Section A, devoted to Physical, Astrono- 

 mical and Mechanical Science, including Engineering, and 

 fourteen gentlemen expressed their willingness to become 

 members. A report of the proceedings of Section A was 

 presented in October last, from which it appears that ten 

 ordinary meetings have been neld, and the following papers 

 read : — 



On November the 4th, a paper on " Trussed Beams " 

 was read by Mr. Pirani. 



On December the 2nd, an essay on " Barometric 

 Levelling" was read by Mr. W. C. Kernot. At this 

 meeting, Mr. Ellery described the methods in use for 

 obtaining uniform rotation, and pointed out the desirability 

 of a more satisfactory solution of this problem. Mr. White 

 invited the attention of members to the question of 

 Barometric Compensation of Pendula of Astronomical 

 Clocks. 



On March the 5th, Mr. Kernot submitted a method for 

 obtaining uniform rotation, which Mr. Ellery undertook to 

 test practically, and to report results. 



