ae 
rivers by the heat of the sun, and its s uent deposit in the 
form of rain on the hill-tops, supplies us with another very large 
raised weight store of energy, and which is practically ut lised 
when the water falling down the hill-side works out water-wheels 
and turbines. 
Various stores of energy arise from the s tion of two 
bodies which desire to come together. ‘he vast fields of coal 
form an enormous store of energy, owing to the tendency of 
carbon to combine with oxygen. Copper which is found pure 
and zinc, when separated from the oxygen with which it is com- 
bined in nature, are examples of the same kind. We may also 
have a store of energy arising from two bodies being too close 
ether, and which desire to move apart ; as, for example, in a 
coiled spring, in compressed gas, in two similar magnetic poles, 
or in two similarly electrified bodies near together. 
The experiments now shown are examples of energy previously 
stored being utilised. This grindstone is being turned by a fall- 
ing weight, the ventilating fan by falling water, this saw is 
worked by the gas-engine, the lathe by this galvanic battery, and 
the sewing machine by three Faure accumulators. 
The water which is falling from the top of the building, and 
which is working this turbine, was really stored in the cistern for 
drinking and washing purposes, and, although serving us as a 
store of energy, it was not pumped up for this purpose. Indeed 
the price charged for water by the water companies would pro- 
hibit its use for the production of power. For, with water at a 
pressure of 100 feet, and at as low a price as 6d. per 1000 gallons, 
it would cost 15. 4d. per horse-power per hour if the turbine had 
80 per cent. efficiency. 
In addition to the natural stores of water-energy on our hill- 
tops, there are also artificial stores of water-energy, or Arm- 
strong’s water accumulators, as they are called, althouzh invented 
long before Sir William Armstrong’s time, and which are em- 
ployed in many large steel works, docks, &c. Water is periodi- 
cally pumped into a cylinder with a heavily-weighted piston, 
which is therefore raised when the water is pumped in. If then 
at any moment, at any part of the works power is required, a 
~ is opened, and this large weight falling at the reservoir 
cy fade drives out the water and performs the desired piece of 
work, 
Now I want to consider how far it would be possible to drive 
a tramear by one or other of these various sources of power, An 
ordinary tramcar for forty-six passengers weighs 24 tons, and 
when full of people about 44 tons, To pull such a carat the 
rate of six miles an hour along an ordinary line requires about 
14 horse-power. To produce such an amount of power for one 
hour requires an expenditure of over 2,800,000 foot lbs of work, 
or if produced by a weight falling say through 10 feet, would 
require the weight to be over 100 tons. 
Armstrong's water accumulators are therefore clearly useless 
for the purpose, and coiled springs are too cumbersome. 
Steam-engines are occasionally employed on tram-lines, and 
from the point of economy are much superior to horses ; but there 
is the great disadvantage of the smoke, noise, and the terror of the 
horses of other vehicles. A detached tramway engine weighs as 
much asa full car, consequently nearly half the tot] horse-power 
employed is used in propelling the engine and boiler, and there 
is also the wa-te of power caused by the rapid radiation of heat 
from the boiler of a small engine. Gas-engines, though saving 
the weight of the boiler and coal, have the compensating disad- 
vantage that per horse-power, the weight of a gas-engine is so 
much greater than that of a steam-engine, and cannot therefore 
at present be economically employed for tram-cars. 
ompressed air engines have been employed with considerable 
success by Col. Beaumont for driving tramears, and he has suc- 
ceeded in storing in one cubic foot of air at 1000 lbs. pressure 
per square inch enough energy to pull three tons about half a 
mile along an ordinary tramway. But successful as this system is 
from the point of economy, there is the same objection that there 
is to the steam tram, viz. the comparative great weight of the 
locomotive. The detached compressed air engine weighs about 
7 tons, while the car full of passengers is hardly 5 tons, so that 
seven-twelfths of the total horse-power expended is employed in 
pulling the compressed air engine alone. I understand it is pro- 
posed to build combined cars and compressed air engines, a 
change that will probably lead to a great improvement, 
In order to obrain mechanical motion, we require a store of 
energy, and some machine for converting the energy stored into 
mechanical work, Now experiment shows thot the weight of an 
electric motor is but a small fraction of the weight of a small 
é ad ee | 
| March 
- 7A. 
steam-engine and boiler per horse-power developed. Electric — 
motors, indeed, can be easily made to vive out work at the rate 
of 1 horse-power per 50 lbs. dead weight of machine, and hence 
the great advantage of using them for movable machinery. [Expe- 
riment shown of drilling holes in thick wood with a hand electro- 
motor and raising large boxes with a smal] electric hoist.] The | 
most economical store of energy we can convert into mechanical 
energy by the agency of electricity is evidently the energy of 
coal, and this is the store we shall mainly employ in driving 
electric motors, That is to say, coal will be burnt to 
mechanical motion, the mechanical motion will work a magneto 
or dynamo electric machine to produce an electric current, the — 
electric current will be conveyed along the wires, and at the 
other end, by means of an electro-motor, the electric current will 
be reconverted into mechanical work. [Experiment shown.] sy 
Instead of converting the electric carrent energy into me-— 
chanical motion I can convert it into heat, and [| shall then 
have, as you see, the ordinary electric light. 
Burt if the engine breaks down, ike electric motor at the other 
end muststop, or the electric light go out ; the constant occurrence 
of which accident has just decided the authorities at the Manche-ter 
Railway Statin to discontinue the use of the electric light. To 
preveit this effect following such an accident, an electric accumu- 
lator is needed, that is a reservoir which has been drinking in the 
electric enerzy when the engine was going at its best, and which 
will now give it out when the engine has stopped. Again, 
apart from accidental fluctuations in the speed of the engine, or 
total breakinys down there is another most important use for the 
electric accumulators. ‘That the electric lighting of towns will 
become general, I need hardly stop to prove to you, and that it 
will be carried out in ways quite different from the expedierts 
temporarily adopted is also equally obvious. But users of electri- 
city in this country have at present to manufacture their electri- | 
city as they require it, and are in the same position that gas-com- 
panies would be in if they were unable to store their gas, but had 
to manufacture it all while it was being consumed. They would . 
evidently require much larger and consequently more expensive 
plant. Now the experience of two years has shown that, for 
large buildings, the electric light is far cheaper than gas. How 
much cheaper will it then become, when the electric energy can 
be manufactured at any time convenient, and stored until it is 
required to be used. 
The earliest form of accumulator was simply a voltameter 
worked backwards. Now althourb Sir William Grove greatly 
increased the efficiency of this secondary battery by coating the 
plates with platinum black, still it was of little practical import- 
ance hecau e of the rapid escape of the greater portion of the 
gases formed, if the charging was continued for a long time, as 
well as their diffusion through the liquid. 
It is clear, then, we must arrange matters so that the passage 
of the primary current, forms on each plate a substance which 
has no tendency to wander over to the other. Such a substance 
must obviously be a solid, and a solid not soluble in the liquid. 
Now, an oxide of lead satisfies, ina marked degree, these con- 
ditions, and hence the employment in secondary batteries of this 
oxide, produced usually by sending an electric current between 
the lead plates immersed in dilute sulphuric acid. 
But, in addition to having the plates near together, they must 
have large surface, in order to store much electric energy. And 
the way to give the plate a large surface, without making it in- 
conveniently larze, is to make it sponzy. Hence what is aimed 
at is two spongy lead-plates near together. 
Planté’s method of accomplishing this occupied some months, 
and even when “ well formed,” his cell does not store very much 
electric energy, so that it has hardly ever been used for any 
commercial purpose. , , 
In 1880, M. Faure thought of the device of putting a thick 
layer of red lead on his lead plates, a substance which can easily 
be reduced to spongy lead by the passage of a current. The 
plates, after being coated with red lead, are then wrapped in 
flannel jackets and put side by side in a box, every alternate 
plate being connected together, so as to practically produce two 
plates with very large surface very near together. To form the 
cells, reverse currents are sent somewhat in the same way that 
| they are sent in forming the Planté cell, with the exception 
that only days and not months are required in the formation. 
The red lead on the one side is reduced to a spongy material, 
which is probably lead very slightly oxidised ; on the other side, 
it is reduced to lead peroxide, Charging the cell, by sending a 
current in the direction of the last current sent, reduces the sub- 
