236 Prof. Lewis, On the measurements of a bead [May 15, 



6' 30'', 6' 30". These threads therefore have been very improperly 

 placed by the opticians (Troughton and Simms) whom I employed 

 for that purpose. The original threads were removed by Mr God- 

 frey. Inequality of intervals might however usefully remove 

 doubts as the position of the instrument when it was employed, 

 whether to the right or to the left of its axis. 



The magnifying powers of the eye-pieces are only moderate. 



The illumination of the field of view is capable of improve- 

 ment. 



A cylindrical zinc cover has recently been made, in two parts 

 fitting each other, so as to protect the instrument from weather, 

 when adjusted on a stone base provided for it on the isolated wall 

 of the Plumian Professor's Observatory. 



May 15, 1882. 



Mr F. M. Balfour, President, in the chair. 



The President announced that the adjudicators for the Hopkins 

 Prize for the period 1871 — 73 had awarded the prize to Lord 

 Rayleigh for his various important papers connected with the 

 Theory of Vibrations, and particularly for his paper on the Theory 

 of Resonance. 



The following communications were made to the Society : 



(1) On the measurements of a bead of platinum, by the late 

 Professor W. H. Miller. By Professor W. J. Lewis. 



[Introduction. Some time ago Mrs Miller entrusted to me 

 the following work of the late Professor Miller, with a statement 

 that he was at work on it at the period when his health finally 

 broke down. The actual measurements were, I believe, all made 

 during the autumn of 1874, and I remember Prof. Miller showing 

 me the arrangement of the goniometers when I came to study 

 with him in September of that year. There is no note of the 

 exact manner in which the upper goniometer was fixed and ad- 

 justed. If the method be again resorted to, the neatest way of 

 arranging the goniometers would be to clamp to the horizontal 



