being used to do other work than charging the accumulators of the
tram-car, the consumption of fuel had to be to some extent estimated. In
the next place, the durability of the accumulators is still to be
ascertained; upon this much of the economy would depend. And in addition
to this question, there is also that of the durability of parts of the
machinery if exposed to dust and mud.

After the electric car, there is no question but that at the Antwerp
Exhibition the most taking of the tramway motors was the Rowan, which was
very economical in fuel, quite free from the appearance of steam, and
very convenient and manageable.

The economy of the Rowan motor arises in a large degree from the extent
of its condensing power, by means of which a considerable supply of warm
water is constantly supplied for use in the boiler, and consequently the
quantity of water which has to be carried is lessened, and the fuel is
economized.

Independently, however, of its convenience as a motor for tramways in
towns, the Rowan machine has been adapted on the Continent to the
conveyance of goods as well as passenger traffic on light branch
railways, and fitted to pass over curves of 50 feet radius, and up
gradients of 1:10.

In England, with our depressed trade and agriculture, there is a great
want in many parts of the country of a cheap means of conveyance from the
railway stations into the surrounding districts; such a means of
conveyance might be afforded by light railways along or near the
road-side, the cost of which would be comparatively small, provided that
the expensive methods of construction, of signaling, and of working which
have been required for main lines, and which are perfectly unnecessary
for such light railways, were dispensed with.

It is certain that this question will acquire prominence as soon as a
system of local government has been adopted, in which the wants of the
several communities have full opportunity of asserting themselves, and in
which each local authority shall have power to decide on those measures
which are essential to the development of the resources of its own
district, without interference from a centralized bureaucracy.

* * * * *

ON THE THEORY OF THE ELECTRO-MAGNETIC TELEPHONE TRANSMITTER.

By E. MERCADIER.

[Footnote: Note presented to the Academy of Sciences, Oct. 19, 1885.]

The first point to be studied in this theory is the _role_ performed