The Sun.
London, England, 1850-05-23 00:00:00

r.of z'nc cost MI, while e, hundred flight of coal
costs but 9d. ; and when to this was added. the reduc-
ion of power in electro magnetism the moment mo-
ion commenced, he had no hesitation in saying 'that
-cost of the la,tter as a motive power would be
:orn 150 to 200 tithes as. grit as that of steam
power. •
An interesting conversation ensued, after which the
thanks of the society were voted to Mr. Hunt, and
the meeting separated. • ,

ROYAL POLYTECHNIC INSTITUTION.
A series of lectures on the 'chemistry of hydrogen,
with special reference to its application for conveying
'by balloons pyrotechnic and other signals to Sir John
Franklin, has been just. commenced by Mr. Pepper,
chemical professor at the institution. After com
meeting on the present doubtful position of the
Arctic Expedition, the audience • was in'ortned
that it was not a lecture on aerostation, the object of
the lecture being to introduce certain ittgenioue
signals invented by Mr. Darby, of Regent street.
Lambeth, which the balloons were to curry. The
materials and construction of the balloons were first
noticed ; as they might be made of oiled silk, gold-
beater's skin, or prepared paper, the letter was pre-
ferred, because with ordinary care it lasted very well,
and had'the great additional advantage of cht-apne,e.
A five-fret gold-beater's Ain balloon cost 10/., whilst
a dozen paper ones could be made for 3/. 16.. ; thus
the number of balloons to be sect might he iticreused,
ip,d the chances multiplied of some of the signals
finding theit way to the missing expedition. The
chemical nature- of hydrogen was then demonstrated
by various experiments, and its extraordinary light-
ness shown by comparison with coal gas. A five•feet
balloon was now sent 'up with Darby's petards or
shelf, which are attached to a fuse or quick match
lined to tithe, and yield a report directly they touch
the ground equal to a 6-pounder cannon, one being
dropped every quarter of an hour. The bill-distri-
butor, to Which so many aeronauts lay claim, was
next. shown, being printed bills which are to be
scattered "as the balloons travel over the range of'
country. The land and water signals next claimed
attention, being composed of gutta percha car, and
cork; and .standing erect on earth or water, :and can
be seen at a-distance of -two miles by an ordinary
telescope, and would be more likely to attract :Wen-
! tion,than the little paper slips. The buoy signals, to
be used in case of distress by the searching party
—the pyrotechnic signals by parachutes—the rocket
signals, and Darby s arrangements for firing, are all
clearly explained. The structure of the ftise or quick
match employed, and its admirable principle (the
argand), was likewise demonstrated ; and it was shown
that it would burn just as well for a few minutes as
for several consecutive hours. Many of the balloons
era on the plan' adopted by Mr. Shepherd, to commu-
nicate with missing voyagers in the arctic regions.
the numerous experiments exhibited by Mr.- Pepper
were_ admirtibly done, illustrating his discourse in a
popular and instructive manner. The lecturer was
greatly applauded at the conclusion of his discourse.