March 29, 1883 | 
when two dynamo-machines (of similar construction) rotated 
nearly at the same speed, but that under these conditions the 
amount of force transmitted was a minimum. Practically the 
best condition of working consisted in giving to the primary 
machine such proportions as to produce a current of the same 
magnitude, but of 50 per cent. greater electromotive force than 
the secondary ; by adopting such an arrangement, as much as 
50 per cent. of the power imparted to the primary could be 
practically received from the secondary machine at a distance 
of several miles. Prof. Silvanus Thompson, in his recent Cantor 
Lectures, had shown an ingenious graphical method of proving 
these important fundamental laws. 
The possibility of transmitting power electrically was so obvious 
that suggestions to that effect had been frequently made since the 
days of Volta, by kitchie, Jacobi, Henry, Page, Hjorth, and 
others ; but it was only in recent years that such transmission 
had been rendered practically feasible. 
Just six years ago, when delivering his pre-idential address to 
the Iron and Steel Institute, the lecturer had ventured to suggest 
that ‘‘ time will probably reveal to us effectual means of carrying 
power to great distances, but I cannot refrain from alluding to 
one which is, in my opinion, worthy of consideration, namely, 
the electrical conductor. Suppose water-power to be employed 
to give motion to a dynamo-electrical machine, a very powerful 
electrical current will be the re-ult, which may be carried to a 
great distance, through a large metallic conductor, and then be 
made to impart motion to electro-magnetic engines, to ignite the 
carbon points of electric lamps, or to effect the separation of 
metals from their combinations, A copper rod 3 inches 
in diameter would be capable of transmitting Icoo h.p. a 
distance of say 30 miles, an amount sufficient to supply one 
quarter of a million candle-power, which would suffice to 
illuminate a moderately-sized town.” This suggestion had been 
much criticised at the time, when it was still thought that elec- 
tricity was incapable of being massed so as to deal with many 
horse power of effect, and the size of conductor he had proposed 
was also considered wholly inadequate. It would be interesting 
to test this early calculation by recent experience. Mr. Marcel 
Deprez had, it was well known, lately succeeded in transmitting 
as much as 3 h.p. to a distance of 40 kilometres (25 miles) 
through a pair of ordinary telegraph wires of 4 mm. diameter. 
The results so obtained had been carefully noted by Mr. Tresca, 
and had been communicated a fortnight ago to the French 
Academy of Sciences. ‘Taking the relative conductivity of iron 
wire employed by Deprez, and the 3-inch rod proposed by the 
lecturer, the amount of power that could be transmitted through 
the latter would be about 4ooo h.p. But Deprez had employed 
a motor-dynamo of 2000 volts, and was contented with a yield 
of 32 per cent. only of the power imparted to the primary 
machine, whereas he had calculated at the time upon an electro- 
motive 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-inch 
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 34-inch diameter, 21,0co h.p. 
might be conveyed to a distance of 300 miles with a current of 
an intensity of $0,000 volts. The time might come when such 
a current could be dealt with, having a striking distance of 
about 1°2 feet in air, but then, probably, a very practical law 
enunciated by Sir William Thomson would be infringed. This 
was to the effect that eleciricity was conveyed at the cheapest 
rate through a convuctor, the cost of which was such that the 
annual interest upon the money expeided equalled 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, aud 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 lightung his house, and of carrying 
on experiments in electro-horticulture from a common centre of 
steam-power. The results -had been most satisfactory; the 
NATURE 
319 
whole of the management had been in the hands of a gardener 
and of labourers, who were without previous knowledge of elec- 
tricity, and the only repairs that had been found necessary were 
one renewal of the commutators and an occasional change of 
metallic contact brushes. 
An interesting application of electric transmission to cranes, 
by Dr. Hopkinson, was shown in operation. 
Amongst the numerous other applications of the electrical 
transmission of power, that to electrical railways, first exhibited 
by Dr. Werner Siemens, at the Berlin Exhibition of 1879, bad 
created more than ordinary }ublic attention. In it the current 
produced by a dynamo-machine, fixed at a convenient station 
and driven by a steam-engine or other motor, was conveyed to a 
dynamo placed upon the moving car, through a central rail sup- 
ported upon insulating-blocks of wocd, the two working-rails 
serving to convey the return current. The line was goo yards 
long, of 2-feet gauze, and the moving car served its purpose of 
carrying twenty visitors through the Exhibition each trip. The 
success of this experiment soon led to the laying of the Lichter- 
felde line, in which both rails were placed upon insulating 
sleepers, so that the one served for the conveyance of the current 
from the power station to the moving car, and the other for 
completing the return circuit. This line had a gauge of 3 feet 
3 inches, was 2500 yards in length, and was worked by two 
dynamo-machines, developing an aggregate current of 9go0o 
Watts, equal to 12 h.p. It had now been in constant operation 
since May 16, 1881, and had never failed in accomplishing its 
daily traffic. A line half a kilometer in length, but of 4 feet 
$3 inch gauge, was established by the lecturer at Paris in con- 
nection with the Electric Exhibition of 1881. In this case 
two suspended conductors in the form of hollow tubes with a 
longitudinal slit were adopted, the contact being made by 
metallic bolts drawn through these slit tube’, and connected 
with the dynamo-machine on the moving car by copper ropes 
passing through the roof. On this line 95,000 passengers were 
conveyed within the short period of seven weeks. 
An electric tramway 6 miles in length had just been com- 
pleted, connecting Portrush with Bush Mills in the north of 
Treland, in the installation of which the lecturer was aided by 
Mr. Traill, as engineer of the Com,any, by Mr. Alexander 
Siemens, and by Dr. E. Hopkinson, representing his frm. In 
this instance the two rails, 3 feet apart, were not insulated from 
the ground, but were joined electrically by means of copper 
staples and formed the return cireuit, the current being conveyed 
to the ear through a T iron placed upon short standards, and 
insulated by means of insulite caps. For the present the power 
was produced by a steam-engine at Portrush, giving motion to a 
shunt-wound dynamo of 15,0co Watts = 20 h.p., but arrange- 
ments were in progress to utilise a waterfall ofample power near 
Bush Mills, by means of three turbines of 40 h.p.seach, now 
in course of erection. The working-speed of thi line was 
restricted by the Board of Trade to 10 miles an hour, which 
was readily obtained, although the gradients of the line were 
decidedly unfavourable, including an incline of 2 miles in 
length at a gradient of 1 in 38. It was intended to extend the 
line 6 miles beyond Bush Mills, in order to join it at Dervock 
station with the north of Ireland narrow-gauge railway system. 
The electric system of propulsion was, in the lecturer’s 
opinion, sufficiently advanced to assure practical success under 
suitable circumstances—such as for suburban tramways, elevated 
lines, and above all lines through tunnels, such as the Metro- 
politan and District Railways. The advantages were that the 
weight of the engine, so destructive of power and of the plant 
itself in starting and stopping, would be saved, and that perfect 
immunity from products of combustion would be insured. The 
limited experience at Lichterfelde, at Paris, and with another 
electric line of 765 yards in length, and 2 feet 2 inches gauge, 
worked in connection with the Zaukerode Colliery since October, 
1882, were extremely favourable to this mode of propulsion, 
The lecturer however did not advocate its prospective application 
in competition with the locomotive engine for main lines of 
railway. For tramways within populous districts the insulated 
conductor involved a serious difficulty. It would be more 
advantageous under these circumstances to resort to secondary 
batteries, forming a store of electrical energy carried under the 
seats of the car itself, and working a dynamo-machine con- 
nected with the moving wheels by means of belts and chains. 
The secondary battery was the only available means of pro- 
pelling vessels by electrical power, and considering that these 
batteries might be made to serve the purpose of keel ballast, 
