The Liverpool Standard and General Commercial Advertiser.
Liverpool, Merseyside, England, 1848-10-10 00:00:00

shop—this very confused attempt to split hairs.]

MEETING OF THE POLYTECHNIC SOCIETY

The monthly meeting of this society took place last night,
at the Royal Institution. The attendance was numerous, and
Mr. W. Bennett, the chairman, presided.

Mr. GRANTHAM then proceeded to read an interesting paper
on the subject of the screw propeller ; and this being a subject
to which Mr. G. has devoted much of his time, and one in
which he has had considerable experience, he was listened to
throughout with marked attention. He illustrated his remarks
by exhibiting several beautiful models and drawings. He
stated that his object on the present occasion was rather to
make a few additional remarks to what he had some years be-
fors stated at this society, than to go through the whole sub-
ject from its origin. He also wished rather to confine his ob-
servations to the screw as an auxiliary power to be employed in
connection with sails, than as an independent power. He ob-
served that the question of screw propulsion had been under a
cloud for some time, owing to the mi-ny discouragements un-
der which the subject laboured. The difficulties, however,
were not connected with the principle, but were owing entirely
to faults in practice. The depressed state of the times was also
much against new projects. Much forbearance on the part of
the public was required—the principle was right—time and ex-
perience would perfect it. Mr. Grantham then drew attention
to the screw, and to several vessels which had continued to
work well for some time, but more particularly to the Sarah
Sands, which, beyond all doubt, he considered to be the most
important case that could be found to test the question of aux-
iliary steam-power as necessary to the merchants' service. She
was now again about to start for America, having crossed the
Atlantic about sixteen times—and if crowds of passengers
and large cargoes were any test of public confidence, she
most certainly possessed a good share of it. She had
preserved great regularity, but owing to her small power,
and being usually very deeply laden, her speed was not great,
unless favoured by the wind, which had not often been
the case. Her qualities were the best displayed in bad
weather. Mr. Grantham made some observations respecting
the government screw-steamers,—immense sums of money
had been expended on experiments and on head-vessels, but
he regretted to say that they had produced nothing that was
likely to lead to improvements in screw propulsion. Mr.
Grantham invited discussion, some remarks were made by the
chairman and others ; but all favourable to his general opinion.
Mr. Smith (of the Gas Company,) paid him a high compliment
on his experience in screw propulsion, and proposed a vote of
thanks to Mr. Grantham, which was carried by acclamation.

.OES'S WATER FILTERERS

Mr. BENJAMIN Hioos, in introducing this subject, said,
that the peculiarity of these filterers was that being attached
to the pipes from cisterns, they were at all times supplied with
water, which they delivered in a pure state, and that too by
self-action. They were also readily cleaned, the operation
being so simple that it might be termed "self-acting." The
idea of drawing water ready filtered was suggested to the
patentee at an eating house in London, where very turbid
water was presented. The waiter stated that they had no con-
venience for the oi- -!ration ; but he himself immediately thought
of a sponge forced into avessel, with a clown stream of water, and
a cock to draw it off. Subsequent experiments led to a variety
of forms of filters, and media of filtration. Woven fabrics of vari-
ous textures were employed, and the inverting of such filters
cleansed them of impurities. In the course of his experiments
he obtained a " second " patent. [Here the lecturer exhibited
four specimens of filters, by one of which 180 gallons would be
discharged in twenty-four hours, sufficient for the supply of
even large establishments.] The substances employed as the
media of filtration were various—pounded granite, quartz,
stone of various kinds, sand, charcoal, &c., separately or com-
bined, as the requirement may be. The cleansing process is
accomplished by the reversing of the stream or flow of water
in its action on the filterers, which are extremely compact, and
formed of Britannia metal. They are, in fact, quite portable
in the hand, and may be attached to any cistern, water-butt,
or pipe. One of them (the most perfect) is constructed with
two taps—one for filtration, and the other for cleansing itself
without unscrewing and inverting. [The only agents in this
town are Mr. Bennett and Mr. Higgs.]
The lecturer's address was listened to with the greatest at-
tention, and, after a brief discussion, a vote of thanks was
passed by the society.

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