with a yield of 32 per cent. only of the energy imparted to the primary
machine, whereas he had calculated at the time upon an electromotive
force of 200 volts, and upon a return of at least 40 per cent. of the
energy imparted. In March, 1878, when delivering one of the Science
Lectures at Glasgow, he said that a 2 in. rod could be made to
accomplish the object proposed, because he had by that time conceived
the possibility of employing a current of at least 500 volts. Sir
William Thomson had at once accepted these views, and with the
conceptive ingenuity peculiar to himself, had gone far beyond him, in
showing before the Parliamentary Electric Light Committee of 1879, that
through a copper wire of only 1/2 in. diameter, 21,000 horse power might
be conveyed to a distance of 300 miles with a current of an intensity
of 80,000 volts. The time might come when such a current could be dealt
with, having a striking distance of about 12 ft. in air, but then,
probably, a very practical law enunciated by Sir William Thomson would
be infringed. This was to the effect that electricity was conveyed at
the cheapest rate through a conductor, the cost of which was such
that the annual interest upon the money expended equaled the annual
expenditure for lost effect in the conductor in producing the power to
be conveyed. It appeared that Mr. Deprez had not followed this law in
making his recent installations.

Sir William Armstrong was probably first to take practical, advantage of
these suggestions in lighting his house at Cragside during night time,
and working his lathe and saw bench during the day, by power transmitted
through a wire from a waterfall nearly a mile distant from his mansion.
The lecturer had also accomplished the several objects of pumping water,
cutting wood, hay, and swedes, of lighting his house, and of carrying on
experiments in electro-horticulture from a common center of steam power.
The results had been most satisfactory; the whole of the management