The Sun.
London, England, 1850-02-14 00:00:00

INSTITUTION OF CIVIL _ENGINEERS.
On Tuesday, Feb. 12 (William Cubitt, Esq., Pre-
sident, in the chair), the first paper read was, "An
Account of the Cast-Iron Lighthouse Tower on
Gibb's-hill, in the Bermudas," by Mr. P. Paterscr.
The site chosen for this tower was in latitude
32 deg. 14 min. N. and longitude 64 deg. .50 min.
IV., being the southern part cf the Bermudas, at
which point they are most safely approached. It was
at first determined to construct the tower with the
materials found in the islands; but, after some pro-
gress had been made in quarrying and dressing the
stone, it was ascertained to be of too friable a nature
fur the purpose, so that the Home Government in-
structed Mr. Alexander Gordon, M. Inst. C. E., to
prepare a design for a cast-iron tower, similar to
that which had been erected from his designs at Alo-
rant Point, Jamaica, and which had proved
very successful. The form cf this tower

• was that of a strong conoidal figure, 105
feet 9 inches in height, terminate d at the top by
' an inverted conoidal figure, 4 feet high, in lieu of a
;
capital
its extreme outside diameter wns 24 feet, at
the narrowest part 14 feet, and at the top 20 feet. Thu
external shell was constructed of 135 concentric cast-
iron plates, having inside flanges, and varying in thick-
ness from one inch at the base to be about three-quarters
of an inch at the top. In the centre of the tower there
was a hollow cast-iron column, 18 inches in diameter
in the inside. and of three-quarter inch metal, fur
supporting Fresnel's Dioptric apparatus, and in
which the revolving weight descended ; it was also
used, in the daytime, for the raising and lowering of
stores, and likewise contained the waste-water pip".
The Icwer part of the tower was filled with concrete,
leaving a well, faced with brickwork, about eight
feet in diameter, and twenty feet in depth, in the
centre. Above this were the seven floors, the two
lower ones being lined with brickwork, and
used as store-rooms, and the upper ones, lined
with sheet-iron, were used as living rooms for the
light-keeper. The details were then given of the
mode a constructing the floors, the windows, the
staircases, and of attaching the lantern and light room
to the main structure; it was stated that the light
was visible from all points of the compass, excepting
when obscured by the high land between Gibb's-hill
and Castle-harbour, from the deck of a vessel et a
distance of about 27 miles, and possibly even at a still
greater distance. The structure occupied less than
one year in its actual erection, the different parts hav-
ing been landed about the end of November, 1844, the
first plate being erected on Gibb's. hill on the 19th of
December, 1844, and the last plate of the tower on
the 9th of October, 1845. The whole cost of the
structure, including the lantern and light apparatus,
was stated to have been about 7,6901., and the annual
expense of maintaining it about 4501.
The next paper read was " A description of Sir
George Cayley's Hot Air Engine," by Mr. W.
W. Poingdestre. After entering briefly into the
theoretical considerations of the expansion of heated
aeriform bodies, and detailing the attempts made by
Lieutenant Ericson, for employing hot air, instead of
steam, as a.prime mover, the author proceeded to
state that, in 1837, Sir George Cayley, dart. Assoc.
Inst. C. E., applied the products of combustion from
close furnaces, so that they should act at once upon a
piston, in a cylinder, similar in every respect to that
of a single acting steam- engine.,The engine consisted
of a generator of heat, a working cylinder, and an air-
pump or blower, the air-pump being half the size of
the cylinder, and blowing air into and through a fire
perfectly enclosed within the generator ; the doors of
the furnace were made perfectly air-tight as soon as
the fire was well got up, the first impulse being given
to the engine, by throwing a few jets of water upon
the fire, which caused the air pump to work im-
mediately, and continued so for hours; the fire being
replenished by stopping off the blast from the furnace,
and opening the upper bonnet. After the air had
passed through the fire, the gaseous products of com-
bustion, generally at a temperature of 600 deg. of
Fahrenheit, passed laterally through a chamber, used
for separating them from any' ashes or cinders, into
the working cylinder before alluded to.
The difficulties attending this description of engine,
were the liability of the working parts to be de-
ranged, by the great sensible heat destroying the
valves, pistons, and cylinders, and carbonising the
lubricating oil. It was stated, that Mr. A. Gordon,
M. Inst. C. E., had made a successful experiment, on
the application of the heated products of combustion
for propelling a boat, without the intervention of any
machinery, between the furnace and the water to be
acted upon.
The paper announced to be read at the meeting of
Tuesday, February 19, was "Description of the Iron
Roof over the Railway Station, Lime-street, Liver-
pool," by Mr. Richard Turner.