32 
POPULAR SCIENCE REVIEW. 
waste in the form of rivers, cataracts, and tidal changes. It is 
remarkable that this mine of potential energy was early worked 
for illuminating as well as motor purposes by the mechanical 
instinct of a great engineer. 
66 A very important application of the electric current,” says 
the “ Daily Telegraph,” “ is now being carried out by Sir William 
Armstrong on his estate, about eighteen miles from Newcastle- 
on-Tyne. The power existing in a volume of water descending 
at the outfall of a Northumberland lake has been utilised by 
the interposition of a turbine, by means of which the requisite 
revolutions are given to a dynamo-electric machine. The 
electric current thus generated is conveyed through a stout 
copper wire to the private residence of Sir William at Cragside 
— a distance of about a mile and a half. The current is there 
conducted through a lamp devised on the Siemens plan, in 
which the regularity of the light is maintained by clockwork, 
subject to the control of an electro-magnet, which magnet 
reflects the strength or weakness of the current, so as to regulate 
the distance between the points of the carbon electrodes. It 
has been found necessary to provide a second wire to take the 
return current, so that the first cost of the light is somewhat 
large, but the working expense is very small. The light is used 
for illuminating the picture gallery at Cragside, and has proved 
eminently successful, not only in respect to the quantity of light 
afforded, but its purity of colour. In addition to this use of the 
electric current as a source of light, Sir W. Armstrong intends 
to avail himself of the power thus brought into his house, by 
applying it to several domestic purposes. This is to be accom- 
plished by means of an electric engine situated in or near the 
house, and receiving the current transmitted from the machine 
at the lake outfall. In this way Sir William will be able to 
make a more constant use of what may be termed his electrical 
6 plant,’ and thus may look forward to a satisfactory result in an 
economical respect. This example of the conversion and trans- 
mission of power will be viewed with great interest, the distance 
of a mile and a half being sufficient to indicate a much more 
extended sphere of action for the electric current than has. 
hitherto been found practicable.” 
Immediately after hydraulic motors comes the steam-engine 
in one form or another. Mr. Shoolbred draws attention to the 
important point of regularity of motion, not only during each 
revolution, but also during successive revolutions. He notices 
the usual precautions of double cylinders, heavy fly-wheels, and 
sensitive governors. Where the motor power required is not 
great, that is, up to about 10-horse power, a gas-engine will be 
found convenient. 
As regards the cost of the Electric Light, Mr. Shoolbred 
