The Sun.
London, England, 1865-12-23 00:00:00

The

,em.

At a very interesting meeting of the Chemical.
Society on Thursday, the subject of the proposed
erection by the British Association Committee in
some of our principal towns of mural standards,
brought forward by Mr. Yates, of Highgate, was
discussed as to the best kind of metal or material
that could be adopted for such purposes.
Mr. WARREN DE 'LA RUE thought it should be
distinctly defined whether the measures proposed to
be erected were intended for extreme accuracy, or
for familiarising the public with the comparisons of
the metre and yard. He regarded Baily's metal as
not being so free from corrosibility as bad been sup-
posed, and suggested that if any metal were to be
adopted, copper would be probably as good as any
for durability, and that the measures themselves
might be electrotyped in highly-finished and polished
moulds, made with the utmost nicety.
Dr. FRANKLAND drew attention to some engraved
plates of white porcelain with scales and letters in
a black material, burnt in by the usual process,
which had been made by Mr. Casella, of Hatton-
garden, for out-door thermometers. These plates
had been exposed for some time to the weather, and
appeared quite uninjured. Porcelain had the ad-
vantage over metal of being far less expansible
or contractible by increase or diminution of tem-

perature.
Mr. S. J. MACKIE spoke of the great need of
some accurate standard of the metre. In three
rules, purchased of some of the best instrument
makers in London, Paris, and Berlin, which he had
that afternoon compared together, there was in a
length of 300 millemetres a difference of 4 of a
millemetre in one, and upwards of a millemetre
in the other. He drew attention to a suggestion
which had been made to him by Mr. Robert Sabine-
of a compensating method for most accura mea
surement, by having one fixed point on the wall and
one movable one working in a slot, and kept in
position by a bar of metal fastened to another fixed
point in the wall, and which metal should expand at
twice the rate of the wall itself. Copper it was
submitted was very nearly perfect in this respect.
The two points giving the exact length of the metre
between them would be thus always kept at exactly
the same distance apart under any variations of
temperature.
Mr. SIEMENS spoke favourably of Mr. Sabine's
suggestion, and considered extreme accuracy in a
standard measure as most important.
Dr. MATTHIESEN considered that the measures
the committee proposed to erect were not likely to

be so extremely accurate as to justify the use of the
term " standards." He thought it would be better
to call them " comparative measures." They would
be quite accurate enough for all practical purposes.
Dr. LEONE LEVI agreed that, as the committee
desired chiefly to familiarise the public with the
new system which had been legalised, it would be
preferable to use the term " comparative measure "
instead of " standard."

Colonel SYKES, M.P., considered that it would

lead to great mischief and litigation if a standard of
a metre were not constructed with the nicest ac-
curacy. There was at present no such standard.
Dr. Miller, Mr. Casella, Mr. Barker, Dr. Mul-
ler, and other gentlemen also spoke as to the diffi-
culty of preserving accuracy under all variations
of temperature in any metallic wall-measure, and
valuable suggestions were made as to the manner and
methods of adjusting the rules compared by artificers
and others with such public measures whenever they
might be erected. '1 ke use of porcelain was
regarded with much favour on account of- its cheap-
ness, the clearness of the black markings and letters
upon it, its durability, and its nearly entire freedom
from perceptible expansion under the influences of
the ordinary variations of climatal temperature ;
and Mr. Casella was requested to prepare some
measurement plates, which he undertook to do at
his own expense.

MARKETS—This Day.

--___Ap.___

COVENT GARDEN.

Fair average supplies of fruit and vegetables are on sale.
in most kinds of produce an active business is passing, at
our quotations :
Fliuu—Pine apples, 8s to 10s; hot house grapes, 3s to
8s ; foreign do, 9d to 2s Od ; filberts, is Gd to 2s Od per lb ;
apples, 2s 6d to 3s 6d per half sieve; new oranges, 4s Od
to lOs ; lemons, 3s 6d to 8s ; walnuts, is to 2s per 100.
VEGETABLES—Red cabbages, is 6d to 2s Od; white do.,
6d to is Od; Savoys, 6d to is Od; celery, 8d to is 9d;
horseradish, 9d to 2s Od per doz heads ; greens, is Gd to 2s
6d; turnips, is 6d to 2s Od ; carrots, as 6d to 45.6 d ; onions,
is 6d to 2s ; brocoli, 4s to 6s per doz bunches ; Brussels
sprouts, is 3d to 2s Od per half sieve ; seakale, is to 2s 6d
per punnet.
POULTRY.

Turkeys, 58 Od to 30s Od ; geese, 6s to 15s Od ;
ducks, 2s 6d to is Gd ; tame rabbits, is Od to 2s Od ; wild
do., is to is 4d; pigeons, Od to Os each; pheasants, 3s Od to
4s Od; partridges, is 6d to 2s 8d; hares, 4s Od to 4s 6d;
grouse, 2s 6d to 3s each ; Surrey fowls, 10s to 14s Od ;
do. chickens, 7s to 9s Od ; barn door fowls, 4s to 9s Od
per couple. English eggs, 14s 15s ; French do., 10s Od
to 12s Od per 100 ; Ostend fresh butter, is 2d to is 5d ;
English is 4d to is 7d per lb.