510 A New Era in Illumination. [ Oct., 
during a period of twenty-seven months have been, exclusive of 
salaries, about one shilling per hour, or inclusive of salaries, two 
shillings.* 
According to a calculation made by the Abbé Moigno respect- 
ing the economy of the light evolved by the French machines, and 
altering the figures to suit the present case, it appears that to main- 
tain a light equal to 4,000 wax candles for one hour, would cost, 
with gas, 10. 2s. 6d.; with Colza oil, 1/. 7s. ; and with the electricity 
produced by a Bunsen’s pile, 1/. 15s. 6d. 
The annual expenditure at a first-class lighthouse, on the old 
system, is on an average 400/. per annum, and on the assumption 
that the light burns for 4,000 hours per annum, that would come 
to two shillmgs per hour. The expenses of the old and the electric 
system are therefore not very dissimilar, and the problem of the 
adoption of electricity to supersede oil, must be decided on grounds 
of convenience and efficiency alone. 
The great advantage of Mr. Wilde’s over the old system of 
magneto-electric machine, appears to be that it is capable of am- 
plification to any required power, by a mere enlargement of the 
size of the different parts. His largest machine weighs about three 
tons. If, instead of using the electric current generated by it to 
produce dynamic effects, we pass it round a still larger electro- 
magnet, we should at once produce a vastly greater development of 
force. The only limit which we see to this multiplication of power, 
is the excessive heat which would be developed in the rotating arma- 
tures. It would be an interesting problem to calculate what would 
be the result of driving the 32-inch armature, required for a 100-ton 
magnet, with (say) a 1,000-horse power steam-engine. If the power 
generated by this machine did not at once burn up the working 
parts, dissipate the electric lamp and conducting wires with a 
mighty explosion into space, and strike dead all the attendants with 
one lightning flash,—if it were at all manageable, and were put ona 
high tower, it would probably give light enough to make London 
by night considerably brighter than London by day. 
Space will not admit of the enumeration of all the uses to which 
so convenient and economical a light may be applied. Moreover, 
this is a subject which has been so frequently discussed that any 
enumeration here would become a mere repetition. One practical 
application has however been made, which possesses great interest. 
Photographers are finding that it is more convenient than the sun. 
According to the ‘Photographic News,’ we learn that an estab- 
lishment has been organized at Manchester, in which is fitted up 
the first of Mr. Wilde’s machines for supplying the electric light. 
By the aid of this, more than two hundred negatives can be ex- 
* ‘Mémoire sur l'KEclairage et la Balisage des Cotes de France,’ par M. L. 
Reyneud, p. 149. Paris, 1865. 
