The Sun.
London, England, 1854-02-23 00:00:00

INSTITUTION OF CIVIL ENGINEERS.

At last week's meeting the paper read was " On the
Principles and Construction of Locks," by Mr. A. C.
Hobbs, Assoc. Inst. C.E.

The author's object was to give a brief review of the
mechanical principles involved in the construction of
locks, and the degree of security hitherto achieved by
manufacturers.

The paper commenced by asserting, as an axiom, that
the highest point of security to be attained in the con-
struction of locks, must consist in the fact, that the pos-
sibility of picking, or opening them, without their true
keys, should depend entirely on chance ; and that not-
withstanding the immense variety of locks already in-
vented, there were really but three absolutely distinct
principles involved in their constrection—so classed
without reference to dates and for convenience of descrip-
tion.

The first principle included all locks having a series of
fixed obstructions, or wards, in and about the key-hole,
to prevent any instrument, except the key, being turned
in the lock ; this principle was shown to be inefficient,
however complicated the construction might be, as the
wards themselves afforded the means of ascertaining the
form of key required to open the lock.
The second principle was that of the letter, or puzzle
lock, which appeared to carry out the principle, or doc-
trine of chance, to the fullest possible extent. But in
this case, also, a method was shown by which the lock
could be opened as easily as in the former ; proving that
the inventor of that class of lock had failed to accom-
plish the object of producing a fastening, whose security
was dependent only on mere chance.
The third principle, or last class of locks, included all
those possessing a series of moveable pieces called slides,
pins,'tumblers, &c., placed within the case of the lock,
and which pieces must be operated upon and moved
into certain given positions by a key before the bolt
could be shot. This principle was illustrated by de-
scriptions of the Egyptian lock, the Bramah lock, the
inventions of Barron and of Bird, the detector of Mit-
chell and Lawton, and the later improvements of Chubb
and of Cotterill (of Birmingham) and others. Allusion
was then made to the great reliance which, until re-
cently, had been placed on these locks, and an explana-
tion was given of the principle on which all locks of
this description could be as easily picked as their pre-
decessors.

The author then commented on the necessity of de-
vising some simple and effective means, by which the de-
fect, common to all the above locks, might be remedied,
without adding materially to the cost. This deside-
ratum he had endeavoured to secure, by the intro-
duction of what was called a moveable stump, which pro.
jection, instead of being rivetted into the bolt, was fixed
to a piece, moving upon a centre, or pin, at the back of
the bolt. The action of that piece was such as to render
it impossible to ascertain the true position of the tum-
blers, for, on any pressure being applied to the lock, for
that purpose, the stump, by its motion, locked the bolt,
and left the turnb:ers at perfect liberty. The author
stated his conviction that this apparently slight altera-
tion rendered it impossible to open such a lock, except
by the mere chance, or accident, of a key fitting it ;
there being no possible means of ascertaining the form of
key requisite to open it surreptitiously. Since the intro-
duction of this lock, several attempts had been made to
produce the same result, without actually copying the
original, but with very little success.
An additional principle of security devised in
America, was then pointed out, in the celebrated
permutating bank lock, invented by Robert Newell,
of the firm of Day and Newall, New York, of
which invention Mr. Hobbs was the proprietor, in this
country. Previois to the introduction of that system,
permutating keys had been used, but they required that
the lock itself shculd be altered, to suit any new adjust-
ment of the bite of the key, whereas, in the American
lock, the key aloue, being altered, produced by its own
action, the corresponding arrangement in the lock ; by
this ingenious contrivance, the person using the lock
became his own lock-maker, and was able to render the
key useless to any other person, by a simple change in
the bits, after locking the door. Such locks, whose
numbers of permutation varied from 720 to 479,001,600,
according to the number of bits in the key, were in-
tended principally for strong rooms of banks, and other
establishments where large amounts of property were de-
posited ; they were, therefore, comparatively expensive,
and were necessarily of larger size than locks required
for ordinary use.
In conclusion, it was remarked, that questions would
continually arise as to the violability or inviolability of
particular locks, and especially of new inventions. The
author, however, claimed to have established that any
new modification or arrangement of the parts of locks,
which did not affect the principle of construction, could
have no particular claim to security, or conversely, that
if it could be shown that any lock was constructed on a
principle not hitherto violated, it might he deemed
secure, but certainly not unless such a claim could be
made good. In respect to the locks alluded to in the
paper, the author justified his statements by the two
facts—that he had not only elucidated the principles on
which all such locks might be picked, but that he had
actually performed all that had been described. Finally,
a hope was expressed that whatever had been done and
said to enlighten the public as to the insecurity of many
locks now in use, instead of causing any unpleasant per-
sonal feelings, would stimulate lock manufacturers to
produce what was really required, viz., secure locks,
adapted to all purposes, of good workmanship and at a
moderate price.

LODGINGS FOR THE POOR.—This plan is take at a
rental ranges of old houses (containing 10 or 12 rooms
each), to convert the staircases of every other house into
lobbies and accessories for each separate floor ; to break
communications through the party walls on every story ;
to clear off and clean the walls ; in some cases to add
a story, or, where the curtilages admit of it, to enlarge
the houses, and in all cases to convert the basement
story into common kitchens, laundries, and cellars. If
the rental of each house, on a repairing lease, be 50/.
(and this for central position is a full allowance ; for
suburban sites it might be 351.), suppose taxes to be
121., add thereto the interest of 1501. per house, as the
outlay on repairs and additions, at 5 per cent., the
total amount is 691. 102., or say 701. a year, for five
commodious suites of apartments, consisting of three
rooms each, with closets, presses, and the other com-
forts of civilized life in higher spheres. This could be
done, then, at 141. a year for each family ; but if you
divide these, perhaps, too spacious and, therefore, too
luxurious suites of chambers in halves, the accommoda-
tion will far surpass anything to be found, not only in
Seven-dials, but even in all Soho (such as are let to
working people), at a rental of only 71. yearly, or about
2s. 81-d. weekly.—. The Builder.

_ .•
POPULATION OF TOWNS AND COUNTIES (IRELAND).—
Some striking and interesting particulars relating to
the population and other social economics of Ireland
are shown in the return moved for by Mr. Fitzroy,
M.P., as to the population of each county, division of
county, and borough in Ireland within the Parlia-
mentary boundaries, and also of the population of each
city and borough returning members to Parliament
within its municipal boundaries.