508 A New Era in Illumination. [| Oct., 
evolved from it was sufficient to cast the shadows of the flames of 
the street-lamps, a quarter-of-a-mile distant, upon the neighbouring 
walls. When viewed from that distance, the rays proceeding from 
the reflector have all the rich effulgence of sunshine. With the 
reflector removed from the lamp, the bare light is estimated to 
have an intensity equal to 4,000 wax candles. A piece of ordinary 
sensitized paper, such as is used for photographic printing, when 
exposed to the action of the light for twenty seconds, at a distance 
of 2 feet from the reflector, was darkened to the same degree, as a 
piece of the same sheet of paper was when exposed for a period of 
one minute to the direct rays of the sun at noon on a very clear 
day in the month of March. The day on which the writer saw the 
machine at work (towards the end of June), the mid-day sun was 
shining brightly in at the window. He took the opportunity of 
roughly comparing the intensity of the sun, with that of the electric 
light armed with the reflector. From a comparison of the shadows 
thrown by the same object, it appeared to him that the electric light 
had between three and four times the power of the sun light. That 
the relative intensities were somewhat in this ratio, was evident 
from the powerful scorching action the electric light had on the 
face, and the ease with which paper could be set on fire with a 
burning-glass introduced in the path of its rays. 
The extraordinary calorific and illuminating powers of the 
10-inch machine, are all the more remarkable from the fact that 
they have their origin in six small permanent magnets, weighing 
only 1 Ib. each, and only capable at most of sustaining collectively a 
weight of 60 lbs. When working up to its full intensity, it requires 
an engine of about 7-horse power to drive it. 
The physicist will, at first sight, consider that the intimate con- 
nection between the consumption of so large an amount of mechan- 
ical power, and the evolution of so enormous an electrical force, is 
a necessary consequence of the modern doctrine of the conservation 
of force. But, without for a moment denying the truth of this 
doctrine, it must be admitted that there are certain phenomena con- 
nected with this machine, which are in apparent contradiction to 
the law of conservation. 
A phenomenon already obtained on a small scale by Jacobi, 
Lenz, and Miers, is rendered visible in the most striking manner 
by means of this machine. When the wires, forming the polar 
terminals of the small exciting magneto-electric machine, were con- 
nected for a short time with those of the large electro-magnet, and 
then disconnected, a bright spark could be obtained, from the wires 
of the electro-magnet, twenty-five seconds after all connection with 
the magneto-electric machine had been broken. 
It will be of interest, apart from all questions as to economical 
production, to ascertain what is the theoretical quantity of coal 
