Scientific American Supplement, No. 312, December 24, 1881 | Page 8

day; but it was got

from diagrams taken during the regular work; then, every half-hour,
when the pressure began to die down, from coal being no longer put
upon the fire, diagrams taken every quarter of an hour, and then toward
the last, every five minutes; and the total number of foot pounds were
calculated from these diagrams, and were used to obtain the gross
indicated horse-power.
Further, so far as could be ascertained by the process of commencing a
trial with a known fire, and closing that trial at the end of six hours,
with the fire as nearly as possible in the same condition, the
consumption was 1.66 lb. of coal per gross indicated horse-power per
hour. So that, without taking into account the coal consumed in raising
steam from cold water, the engine worked for 1-2/3 lb. of coal per
horse per hour. I think it well to give these details, because undoubtedly
it is an extremely economical result.
ETHER ENGINE.
Our president alluded to the employment of ether as a means of
utilizing the heat which escaped into the condenser, and gave some
account of what was done by Mons. Du Tremblay in this direction. It
so happened that I had occasion to investigate the matter at the time of
Du Tremblay's experiments; very little was effected here in England,
one difficulty being the excise interference with the manufacture of
ether. Chloroform was used here, and it was also suggested to employ
bisulphide of carbon. In France, however, a great deal was done. Four
large vessels were fitted with the ether engines, and I went over to
Marseilles to see them at work. I took diagrams from these engines, and
there is no doubt that, by this system, the exhaust steam from the steam
cylinder, which was condensed by the application of ether to the
surface of the steam condenser (producing a respectable vacuum of
about 22 inches), gave an ether pressure of 15 lb. on the square inch
above atmosphere, and very economical results as regards fuel were
obtained. The scheme was, however, abandoned from practical
difficulties. It need hardly be said that ether vapor is very difficult to
deal with, and although ether is light, the vapor is extremely heavy, and
if there is any leakage, it goes down into the bilges by gravitation, and

being mixed with air, unless due care is taken to prevent access to the
flues, there would be a constant risk of a violent explosion. In fact, it
was necessary to treat the engine room in the way in which a fiery
colliery would be treated. The lighting, for instance, was by lamps
external to the engine room, and shining through thick plate-glass. The
hand lamps were Davy's. The ether engine was a bold experiment in
applied science, and one that entitles Du Tremblay's name to be
preserved, and to be mentioned as it was by our president.
THE QUICKSILVER ENGINE.
These was another kind of marine engine that I think should not be
passed over without notice; I allude to Howard's quicksilver engine.
The experiments with this engine were persevered in for some
considerable time, and it was actually used for practical purposes in
propelling a passenger steam-vessel called the Vesta, and running
between London and Ramsgate. In that engine the boiler had a double
bottom, containing an amalgam of quicksilver and lead. This amalgam
served as a reservoir of heat, which it took up from the fire below the
double-bottom, and gave forth at intervals to the water above it. There
was no water in the boiler, in the ordinary sense of the term, but when
steam was wanted to start the engine, a small quantity of water was
injected by means of a hand-pump, and after the engine was started,
there was pumped by it into the boiler, at each half revolution, as much
water as would make the steam needed. This water was flashed on the
top surface of the reservoir in which the amalgam was confined, and
was entirely turned into steam, the object of the engineers in charge
being to send in so much water as would just generate the steam, but so
as not to leave any water in the boiler. The engines of the Vesta were
made by Mr. Penn, for Mr. Howard, of the King and Queen Ironworks,
Rotherhithe. Mr. Howard was, I fear, a considerable loser by his
meritorious efforts to improve the steam-engine.
There was used, with this engine, an almost unknown mode of
obtaining fresh water for the boiler. Fresh water, it will be seen was a
necessity in this mode of evaporation. The presence of salt, or of any
other impurity, when the whole of the water was flashed into steam,

must have caused a deposit on the top