518 The British Association. [October, 
pressure equal to a column of water 6 inches high, to 
maintain a small jet in the lantern on each beacon. The 
high pressure prevented the jet from being blown out by the 
wind, and the arrangement which he had devised enabled 
the operator to turn on the flame or diminish it to a small 
jet as easily as the same result could be accomplished in 
the case of an ordinary light in a dwelling-house, but by 
using exactly opposite means, i.e., the gas was turned off 
to be lighted and turned on to be extinguished. 
Mr. Wigham also read a short paper on “ Fog Signals.” 
He proposes to use the gas available in lighthouses for gas 
guns. The report is caused by the explosion of the mixture 
of oxygen and coal-gas. The gun may be fixed on a rock 
in the sea at a considerable distance from a lighthouse or a 
fog-signal station, and will be lighted and fired as often as re- 
quiredfrom the station, withoutthe keepers leavingtheirpost. 
A third paper was read by Mr. Wigham “ On a New 
Atmospheric Gas Machine,” which the inventor claimed 
was admirably adapted for places where coal-gas is difficult 
of application, as in country houses at a considerable distance 
from towns. When two burners of the same size were 
lighted, the one with ordinary gas and the other with atmo- 
spheric gas, it was difficult to tell which was the brighter or 
clearer. Mr. Wigham said it required neither fire nor retorts 
nor gas-holders ; no special knowledge was necessary on the 
part of the person who attended to it, and the products of 
its combustion were as harmless as those evolved from the 
purest wax. It would not tarnish silver or injure the deco- 
rations of any furniture. 
Mr. G. J. Stoney read a “ Report on the Oscillation- 
Frequencies of the Rays of the Solar SpeCtrum.” The 
report shows that so long as light is propagated through a 
vacuum the undulator, however complex, maintains its form 
unaltered at all distances from the source of light ; for in 
vacuous spaces waves of different periods advance at the 
same rate and direCtly forward, and therefore the simple 
component undulations which are represented by the several 
terms of a sinusoid series accurately accompany each other 
throughout their whole journey. But the event is different 
if the light encountered an optical agent which aCted 
differently on waves of different periods. Of this kind were 
the prisms and diffraCtion-gratings of our spectroscopes. 
Waves of different periods are compelled to travel in different 
directions, and thus the several terms of the sinusoid series 
appear under the form of lines in the speCtrum. The wave- 
