58 Scientific Intelligence. 
ter of great importance in light-houses. In the model the car- 
bons are 15mms. on a side and yet notwithstanding their large 
size the sensibility of the apparatus is so great that a small rin 
of rubber placed between the two carbons is capable of arresting 
the motion without undergoing a sensible change in form.— Comp- 
tes Rendus, \xxxii, 1054. B® 
16. Electro-magnetic Rotations.—Mr. W. Sporriswoope in 4 
nomenon known as the rotating spark. A powerful magnet being 
The discharge, as is well known, consists of two parts, the 
spark proper and a bright cloud or flame surrounding it which 
tile chlorides to flow across the field of action. The following 
. Supposing the magnetic fie 
during the greater 
again as the discharge fall, 
€ axis. 
nerating line. The appearance of the discharge when 
viewed in a revolving mirror confirms the above remarks.— 
Nature, xiii, 698, E. © P. 
