570 Royal Institution. 
gularities, on the edge of the disc, produce distinct beads. Professor 
Powell has tried a similar experiment with the circular opake disc 
and the rays of the sun reflected from a small piece of glass, which 
produced a most brilliant ring, the dise being nearly double the ap- 
parent diameter of the sun: and he proposes to pursue the inquiry 
still further. ——_—_. 
MEETING OF THE ROYAL INSTITUTION. 
Friday, June 9, 1843. 
The lecture was by Professor Faraday, on the “Electricity of 
Steam.” The Professor commenced his lecture by illustrating the 
extent of our knowledge of the electricity which accompanies the 
formation of steam previous to the observations about to be detailed, 
showing that when water is poured into a heated metal cup electri- 
city was set free; and that if the vessel, into which the water was 
placed, was above a certain elevated temperature, no electricity was 
evolved in consequence of the water being prevented from contact 
with the containing vessel by a stratum of steam. The Professor 
then detailed the first observations made at Newcastle by one of the 
workmen in attendance on a boiler belonging to the Newcastle and 
Carlisle Railway, and whose report, that the boiler was full of fire, 
from the fact that when he placed his hand near it an electric spark 
was communicated, drew the attention of Mr. Armstrong to the 
subject, the result of whose investigations was then given. A boiler 
having been arranged for the purpose of illustrating this subject, the 
Professor exhibited the production of the spark during the emission 
of the steam, and showed most conclusively that the boiler and 
appendages were charged with negative electricity, while the issuing 
steam was in the opposite or positive state; that it was necessary 
that the boiler should be insulated; that the steam should issue 
through a small aperture; that the material of which this aperture 
was constructed modified materially the quantity of electricity, wood 
and the metals having been found by experiment to be the best 
fitted for the purpose ; that the introduction of a small portion of 
saline matter, as sulphate of soda, into the exit chamber prevented 
entirely the elimination of electricity, and even when common 
water was introduced it had the same effect; that by long con- 
tinuance of the issuing current of steam, electricity was gradually 
developed, from the condensed steam displacing and driving out the 
saline matter, pure water being a necessary element for its produc- 
tion; and that the whole phenomena arose from the rubbing of the 
condensed water against the tube from which the steam was issuing. 
The Professor also proved that the introduction of ammonia reversed 
the electrical states, what was before negative becoming positive, 
and that as the ammonia was expelled the original states were gra- 
dually restored ; that turpentine and acids acted in the same way as 
saline substances, from their enveloping the particles of water in a 
film of their own substance. The lecturer considered, from these 
facts, that the view advocated by Mr. Armstrong, that the electricity 
arose from the passage of water into the aeriform state, was not 
tenable, and that the thunder-cloud and the lightning’s flash could 
not be attributed to this origin. 
