518 
Notes. 
little of the force exerted on the spindle is to be communicated 
to the diaphragm, and the time when that force is to be brought 
into play, and it may, mechanically speaking, be compared to a 
frictional clutch, coupling a machine to a steam-engine, and 
which, at any moment, may be made to transmit the full power 
of the motor to the machine, or, by reducing the friction, to 
transmit only a portion of that power. 
The Parliamentary Committee on Electric Lighting have con 
eluded their labours and issued their report. We shall refer to 
the evidence in a future number of this journal. In their report 
the Committee state that the general nature of the elecftric light 
has been well explained in the evidence of Prof. Tyndall, Sir 
William Thomson, Dr. Siemens, Dr. Hopkinson, and others. 
It is an evolution of scientific discovery which has been in aeftive 
progress during the whole of this century. Essentially the 
elecftric light is produced by the transformation of energy either 
through chemical or mechanical means. The energy may be 
derived from a natural force, as, for instance, a waterfall, or 
through combustion of a material in the cells of a voltaic battery, 
or of fuel in a furnace. The energy being converted into an 
elecftric current, maybe used to manifest elecftric light by passing 
between carbon points, or by rendering incandescent solid bodies, 
such as iridium. A remarkable feature of the elecftric light is, 
that it produces a transformation of energy in a singularly com- 
plete manner. Thus the energy of one-horse power may be con 
verted into gaslight, and yields a luminosity equal to 12-candle 
power. But the same amount of energy transformed into 
elecftric light produces 1600-candle power. It is not therefore 
surprising that while many praeftical witnesses see serious diffi- 
culties in the speedy adaptation of the elecftric light to useful 
purposes of illumination, the scientific witnesses see in this 
economy of force the means of great industrial development, 
and believe that in the future it is destined to take a leading 
part in public and private illumination. There is one point on 
which all witnesses concurred, that its use would produce little 
of that vitiated air which is largely formed by the produefts of 
combustion of ordinary illuminants. Scientific witnesses also 
considered that in the future the elecftric current might be ex- 
tensively used to transmit power as well as light to considerable 
distances, so that the power applied to mechanical purposes 
during the day might be made available for light during the night. 
So far as the praeftical application of the elecftric light has already 
gone there seems to be no reason to doubt that it has established 
itself for lighthouse illumination, and is fitted to illumine large 
symmetrical places, such as squares, public halls, railway stations, 
and workshops. It is used in Paris for lighting shops which 
require a light by which different colours may be distinguished, 
and has recently been used in England for the same purpose 
with satisfactory results. 
