164 General Monthly Meeting. [Feb. 4, 



exhibited, for the purpose of proving experimentally some of the 

 assertions made by the speaker in reference to this subject. A 

 cube of bismuth was taken and suspended by a twisted string 

 between tlie two poles of an electro-magnet. The cube was at- 

 tached by a short copper wire to a little square pyramid, the base 

 of which was horizontal, and its sides formed of four small triangu- 

 lar pieces of looking-glass. A beam of light was suffered to fall 

 upon this reflector, and as the reflector followed the motion of the 

 cube the images cast from its sides followed each other in succes- 

 sion, each describing a circle of about 30 feet in diameter. As the 

 velocity of rotation augmented, these images blended into a con- 

 tinuous ring of light. At a particular instant the electro-magnet 

 was excited, currents were evolved in the rotating cube, and the 

 strength of these currents, which increases with the conductivity 

 of the cube for electricity, was practically estimated by the time 

 required to bring the cube and its associated mirrors to a state of 

 rest. With bismuth this time amounted to a score of seconds or 

 more : a cube of copper, on the contrary, was struck almost instantly 

 motionless when the circuit was established. 



[J. T.] 



GENERAL MONTHLY MEETING, 



Monday, February 4. 



William Pole, Esq. M.A. F.R.S. Treasurer and Vice-President, 

 in the Chair. 



George Busk, Esq. F.R.S. F.R.C.S. 



Major-General Anthony Emmett, Royal Engineers, and 



William Baker Taylor, Esq. Surgeon-General, Bombay Array, 



were duly elected Members of the Royal Institution. 



Thomas Farquhar Hill, Esq. and 

 Jonathan Rigg, Esq. 



were admitted Members of the Royal Institution, 



The following Presents were announced, and the thanks of the 

 Members were returned for the same : — 



From — 

 H.R.H. Prince Albert, K.G. F.R.S. Vice-Patron, i?./.— W. Macgillivray, 

 Natural History of Dee-Side and Braemar. Edited by E. Lankester, M.D. 

 8vo. 1855. 



