uminum industry.

Aluminum is, in Berlin, generally used pure, and cast pieces only are
composed of aluminum containing about 5 per cent of silver.

Nevertheless the use of aluminum will remain limited, even in case the
cost of manufacturing it could be materially reduced, until some
method shall have been discovered by which aluminum may be soldered.

This difficulty has, in spite of all efforts, not yet been overcome,
and for some purposes, to which the metal would otherwise be well
adapted, it remains so far unavailable. Here then is a chance for some
ingenious mind.

* * * * *

AN IMPROVED DOOR BOLT.

The accompanying engraving represents, in perspective and in section,
an improved door bolt, recently patented by Mr. Thomas Hoesly, of New
Glaras, Wis.

The principal features of this bolt will be understood by reference to
the engraving. On the plate or body are cast two loops or guides for
the bolt, and the plate is slotted under the bolt, and a lug projects
into the slot and bears against a spring contained by a small casing
riveted to the back of the plate. The end of the bolt is beveled, and
its operation is similar to that of the ordinary door latch. Two
handles are provided, one of which is of sufficient length to reach
through the door, and a pawl or dog accompanies the bolt, which may be
attached to the door with a single screw, and is to be used in locking
the door. The bolt is very simple and strong, suitable for shops,
out-buildings such as barns, stables, etc., and some of the doors of
dwellings.

[Illustration: HOESLY'S DOOR BOLT.]

Further information may be obtained by addressing the inventor, as
above.

* * * * *

CHIMNEY FLUES.

Messrs. W. H. Jackson & Co., of this city, whose long experience in
treating refractory flues gives weight to their opinion, communicate
to the _American Architect_ the following useful information:

To secure a good draught the chimney should be of sufficient size,
should be carried up above surrounding objects, should be as straight
as possible throughout its length, and should be as smooth as possible
inside, to avoid friction. As a draught is caused by unequal
temperatures, the chimney should be so arranged as to avoid a rapid
radiation of heat. If in an exterior wall there should be at least 8
inches of brickwork between the flue and the exterior surface. For
country houses it