The Express.
London, England, 1851-02-08 00:00:00

LONDON, SATURDAY EVENING, FEBRUARY 8, 1851.

the case of woods, indeed, not only was all that was
already known regarding them attempted to be
collected, but experiments were in many cases made
on purpose, with the view of extending our know-

MACHINERY IN PREPARATION.

3IFSSIt9. PENN, or GREENWICTI.

The contributions from the eminent engineering
firms in London and the neighbourhood will not be so nu-
merous and important as they ought to be. Many of them
entertain the opinion that their fame is so well established
that it is unnecessary to court publicity by any display of
their works, whilst others consider it would be of little in-
tereat to exhibit models of machinery that possess no novelty
in construction or design; overlooking the fact that a main
object of the Exhibition is to show the various products of
national industry, whether they be new or already known.
Foremost among those who take a more enlarged view of
the objects of the show of industry, are the Messrs. Penn,
of Greenwich, who will be probably the largest exhibitors
of machinery. They have now nearly ready a pair of
marine paddle-wheel steam-engines. of twelve horse-power
each, which will illustrate, on a small working scale, the
perfection attained in the construction of such engines.
This pair of engines will, we understand, be kept at work,
tar the disables purpose of exhibiting their action and of
supplying some of the steam power that will be requisite
fur driving the various mechanisms to be exhibited in motion.
Messrs. Penn have also in preparation a pair of 30 horse-
power marine steam-engines for driving a screw propeller,
which we believe will be completed in time for the Exhibi-
tion. In addition to these engines, which will occupy a
Large portion of space, a great number of highly-finished
models will be contributed by the same firm, who seem to
take great interest in the success of the Exhibition, and to
be determined that nothing shall be wanting on their part
to effect o proper representation of the engineering skill of
the country.
With respect to the working of engines in the Crystal Palace
the question arises, what is to be done with the 'rime
steam ? Marine engines are, in this country, made with-
out exception on the condensing principle, and are worked
with steam at low pressure, that is to say, instead of em-
ploying the elastic force of steam to move the piston the
principal agent is the pressure of steam of comparatively
small elastic force acting against a partial vacuum caused
by the condensation of steam in a condenser. To produce
an efficient condensation a large quantity of constantly re-
newed cold water is required, for which purpose a pond is
often seen near to the engine-houses of factories where con-
densing engines are employed, and the water in those ponds
generally indicates the object for which it is employed by
the vapour arising from its surface, the water having been
warmed by the process of condensation. As in all pruluibi-
lity there will be several condensing engines employed at
the Crystal Palace, there will consequently be an ample
supply of warm water, oral it may be worth considering
whether it can be applied to any use. If allowed to flow
into the Serpentine, that so-called " river " might fur the
time be converted into a tepid swimming bath.

MEsShLs. MAI:DALAII4 AND FIELD.

Megan. Maud.lay and Field intend to exhibit aateam-

engine of six-horse power, to be employed in working a
coining press on a new construction, The mode by which
the impression on the metal is produced, and the method of
working is different from any that has hitherto been
adopted, and the sight of the press in action will form an
interesting feature of the Exhibition. We understand that
the Executive Committee have not yet determined on what
principle the press shall be worked. It has been proposed
that it should be employed in stamping medals, impressed
with an appropriate design, to Ix, sold within the building,
the proceeds to be at the disposal of the Commi-sioners ;
but the sale of anything beyond refreshments within the
precincts of the Crystal Palace has been so forcibly prohi-
bited in the rules hitherto published, that the Executive
Committee are reluctant to depart from them; at the same
time, it is felt that much of the interest attached to the p.es-
session of such medals would depend on having seen them

come from the press. The Committee arc thus on the horns
of a dilemma ; but it is very probable that in this, and in
some similar CASE.] that must arise, exceptions will be
made, under proper regulations, to the general rule.
Messrs. Maudsloys and Field, in addition to the coining-
press, intend to contribute several models of different kinds
of machinery and engines, which will form an illustration
in little of many of the important works they have com-
pleted.

GIGANTIC ELECTRIC CLOCX‘.

Time in the Crystal Palace will be regulated by several
electric clocks, of large dimensions, made by Mr. C. Shep-
herd, of Leadenhall-street, on the improved plan recently

invented by Mm. The largest of these clocks will be on the
outside of the building, ever the northern entrance to the
transept, and the appearance of the dial and hands will be

quite as novel us the interior arrangements. The diameter
of the dial will not be less than twenty-four feet, but it will
only be a semi-circle, for it was found that a complete dial
of that size would detract from the appearance of the build-
ing. Mr. Shepherd had the option of having a circular
dial of seven feet diameter, but that he considered would
be too insignificant for the purpose, and he preferred the
larger dial, with its semicircular proportion. There will not,
indeed, be any clock-face, such as we are accustomed to see,
but the hours will be painted in compartments, on the arch of
the transept, the Roman numerals appearing white on a blue
ground. The twelve hours will be included in the semi-
circle, beginning with VI on the left hand, ascending to
XII at the top of the arch, and descending to VI on the
right. That the hands may indicate the time at all hours
of the day and night, they are made double, so as to point
both ways ; thus, when the hour-hand has arrived at six in
the evening, it will more off the dial on the right, and the
opposite end of the hand will become the index to the hours.
In the same manner, the opposite end of the, minute-hand
will recomntenee its duties as index every hour, and then
again pass off the dial. In the intermediate times, the
double part of the hands, though of no use in pointing out
the hours, will serve the important offices of equipoises and
counteracting vanes, to equalise the force of the wind; for,
without some such provision, the wind, acting on a lever ten
feet long, might have impeded the action of the clock, or
have caused irregularity. The length of the double minute-
hand will be about twenty feet, and that of the hour-hand
sixteen feet, to be mule of gilded copper. In addition to
this monster clock, there will be two electric clocks, with
circular dials, five feet in diameter, placed inside the eastern
and western entrances, and other smaller ones in different
parts of the building, all Of which will be of similar con-
struction, and will all be in connection with and regulated
by the same pendulum.
The distinctive feature of Mr. Shepherd's electric clocks
consists principally in the mode of giving impulse to the
pendulum. In the electric clocks previously constructed,
the pendulum at each vibration touched a metal stud in
connection with a voltaic battery, and by that means
communicated instantaneous but temporary magnetism
to a coil of wire enclosed within the bob of the pendu-
lum, and caused it to be attracted by a combination of per-
manent steel magnets placed within the sphere of attraction.
The impulse to the pendulum was consequently derived
from repeated magnetic attractions ; and, as voltaic batteries
are constantly liable to variation, the movement of the
clocks varied accordingly. In Mr. Shepherd's arrangement
the impulse is given to the pendulum by a spring, and the
electro-magnetic power is employed only to relieve the pen-
dulum from the action of the spring during the:return of
vibration. By this means the impulse is altogether inde-
pendent of the varying power of the battery, and the action
is constantly the same. Another part of Mr. Shepherd's
improvement consists in the mode of giving motion to
the hands, which are made distinct from the
pendulum, and thereby another cause of irregu-
larity is avoided. The pendulum is, indeed, detached
completely from the mechanism, its sole use being confined
to regulate the passage of the electric currents. An ordi-
nary second pendulum, of the size used in an eight-day
clock, is all that is necessary to put in action the largest
electric clock, and a pendulum of that size will be employed
for working the great clock at the Crystal Palace and all
the other clocks in connection with it. The detachment of
the different parts of the same clock from each other, yet
the connection that exists between separate clocks at consi-
derable distances apart, constitute a remarkable feature of
the invention. The pendulum may be hundreds of yards
from the clocks it regulates, the striking arta luay-be

twenty of ruck clocks is so intimate that tocy wilt al, re-
spond instantaneously to the vibration of atingle pendulum,
and move invariably together. The battery power required
is very feeble, and we understand that one of Mr.
Shepherd's clocks, made on this principle, has been going
for two years without requiring to be touched, or having
the battery renovated.