much interest in London at the time the Argyle Rooms were on fire. A
similar engine of greater power was subsequently constructed by
Ericsson and Braithwaite for the King of Prussia, which was mainly
instrumental in saving several valuable buildings at a great fire in
Berlin. For this invention Ericsson received, in 1842, the large gold
medal offered by the Mechanics' Institute of New York for the best plan
of a steam fire-engine.

In the year 1833 Ericsson brought before the scientific world in London
his invention of the Caloric-Engine, which had been a favorite subject
of speculation and reflection with him for many years. From the
earliest period of his mechanical labors, he had been in the habit of
regarding heat as an agent, _which, whilst it exerts mechanical
force, undergoes no change._ The steam in the cylinder of a
steam-engine, after having lifted the weight of the piston, contains
just as much heat as it did before leaving the boiler,--minus only the
loss by radiation. Yet in the low-pressure engine we turn the steam,
after having performed its office, into a condensing-apparatus, where
the heat is in a manner annihilated; and in the high-pressure engine we
throw it away into the atmosphere.

The acting medium employed in the Caloric-Engine is atmospheric air;
and the leading peculiarity of the machine, as originally designed by
Ericsson, is, that by means of an apparatus styled the Regenerator the
heat contained in the air which escapes from the working cylinder is
taken up by the air which enters it at each stroke of the piston and
used over and over again.

The machine constructed by Ericsson in London was a working engine of
five-horse power, the performance of which was witnessed by many