25 
from which it is insulated. The coils of the electro-magnet 
are thus placed in the same circuit as the carbon pencils. 
When the alternating current from an electro-magnetic 
induction machine is transmitted through the carbons, the 
electro-magnet attracts the armature and separates the 
upper ends of the carbons, which brings them into their 
normal position, and the light is immediately produced. 
When the circuit is interrupted, the armature is released : 
the upper ends of the carbons come into contact, and the 
light is produced as before. When several pairs of carbons 
are placed in the same circuit, they are, by this arrangement, 
lighted simultaneously. 
MICROSCOPICAL AND NATURAL HISTORY SECTION. 
October 7th, 1878. 
Charles Bailey, Esq., President of the Section, in the 
Chair. 
Professor W. C. Williamson, F.RS., made remarks on 
a series of Lepidodendroid Macrospores from the Halifax 
Coal Measures, as well as a series of reproductive crypto- 
gamic conceptacles from the same measures, and also exhi- 
bited some of these under the new Oil Immersion Lens of 
Zeiss of Yena, 
Mr. Plant exhibited a so-called Tree Onion from Canada. 
