Pittsburg dispatch. [volume] (Pittsburg [Pa.]) 1880-1923, 1892-02-24
SCRAPS OF SCIENCE
Some Recent Novel Innovations in
the Mechanical World.
IMPORTANT USE FOR COAL TAR.
The Application Of the Sand Blast in
English Practice.
UNIQUE THEORIES ON VARIOUS TOPICS

Coal tar has recently come into extensive
use as a means of rendering masonry i'm
| pervious to water, especially in positions
exposed to direct contact with water Tar
used to coat masonry built up of extremely
porous stone renders it quite impervious
even at depth of so feet of water, as our
| experience over many thousands Of square
yards distinctly bears out. Tar, used as
will presently be explained, ought to be
utilized in all public buildings, particularly
those designed for the preservation of works
of art; for the dissolving, action of water
| upon mortar even of excellent quality is
well known, and also the disagreeable con-
| sequences of the exudation of water charged
with lime salts from the mortar.
The tar may be employed in two different
ways: it may be used in boiling state in
one or several layers, or 1t may be made to
flame up before it is used. The first method
is suitable for surfaces exposed to the air.
the second is appropriate to surfaces which
have to be covered up. When boiling coal
tar is used in three coats on masonry, the
result is black and very brilliant varnish,
which perfectly resists the action of frost,
water and sun, and which is absolutely i'm
pervious. Its good effects last many years.
and in many cases the use of layer of
plaster or cement is rendered unnecessary.
By adding to the coal tar an india-rubber
paste, produced by dissolving rubber clip
pings in benzine or petroleum, coating
may be obtained which is still more resistant,
elastic and durable. The tendency of the
black coating to absorb heat may be over
come by white-dusting the whole before the
tar is quite dry; the white adheres and the
heat is reflected.
A most unique combination Of mechanical
and nautical skill, in its way, is the passen-
ger car transfer ferryboat which for some
time past has been operated in the Straits of
Mackinac by the Duluth. South Shore and
Atlantic Railroad. As described, it has an
enormous capacity for carrying cars, but its
peculiarities are its strength, its shape and
the number of its steam engines. 1t carries
"a steam engines for performing the various
requirements of the business in hand. The
hull of the boat is q triumph of solidity,
and the bow rises up and away from the
water, so as to hang or slant over it. .as if it
were hammer-what, indeed, 1t is designed
to be; this is because the boat is an ice
breaker, intended to keep channel open in
the straits all winter, or to make one when
ever 1t is necessary to encounter the massive
Ice Gnab IOIuls III tndt cOiu region, tue Dig
boat advancing toward the ice, and, showing
its nose upon the edge, lifting herself upon
it. Then screw propeller under the over
hanging bow performs the work of sucking
the water from under the ice to enable the
boats weight to crush it down the more
easily. Thus the monster makes its way
steadily through the worst ice of the semi
polar winters of that region, climbing upon
the ice, crushing it down, and scattering it
on either side.
The peculiar fact is remarked upon in the
Engineering Journal that, as compared with
English practice, the sand blast process has
found but little favor in the United States, a
single company in Sheffield using at least
200-horse power of steam in its operations,
and the application elsewhere in Europe
being extensive for various purposes In
Sheffield the main utilization in this line is
the recutting of new files to improve them.
The process is familiar by which files are
cut with chisels that raise up shavings or
teeth, these being of curved form
and with q thin edge that soon
crumbles or breaks, unless the cutting is
skillfully done and the steel of good quail
ity. When treated by the sand blast the
impinges on the back Of the teeth, cutting
away the thin edge but not affecting the
face, the teeth thus becoming strong cut
ters without the thin curled edge left BY the
chisels in cutting. The operation is very
rapid, requiring but a few seconds, and the
value of the files is much increased. Sand,
however, in the common sense, is not en-
ployed in this process, but mixture of
sandy clay and water, thin enough to be cir
culated by pumps. This mixture of clay
water, as it may be called, is drawn in by
induction nozzles and, discharged through
thin slit made in chilled cast iron tips that
wear away very rapidly.
In the basement of downtown restau- |
rant there is queer looking array of cylin-
ders connected by pipes They don't move
nor make any noise, but they perform a |
great amount of work that can hardly be |
appreciated. They are connected on the |
one hand with steam boilers in an adjacent |
room, and on the other hand, leading from |
them up in the air, is a 4-inch pipe. Two |
of the big cylinders contain ammonia This |
is turned into gas by the action of steam
and conveyed into smaller cylinders at the |
side, which act as storage reservoirs. Lead |
inch pipe, that goes along the ceiling for a
hundred feet, and then turns upward, con-
Meeting with 7l-inch pipes that run into
refrigerator. These A-inch pipes are COW
cred with frost to thickness<f quarter
of an inch, and in the refrigerator coil of
the pipe produces so much cold that
the thermometer sometimes goes down to
zero. 1t Is not the intention to keep the |
as cool as this, but in the ex-
periments that have been carried on no
effort was made to restrict the amount of
cold produced. After the gas leaves the re-
frigerator it turns back again into ammonia
and flows back to the big cylinders below to
be changed again into gas when required.
There is also big chest filled with brine
downstairs. Pipes are carried into this
brine and in a very short time water in cans |,
is turned into blocks of ice. Ali this work
is done without expert attention and about
The only labor connected with the making
of ice and cold is the turning on or off of
few valves. Messrs G. H. Abel and j. H.
Gordon, who have been Investigating the
process, have about decided that they will
refrigerate the market by this process They
are satisfied as the result of the experiment
at Dimling's that they can make more cold
than the ice companies and at a less expense
Mr. Abel thinks that the gas could be car
ried in pipes from one part of the city to
smother, and that he could produce cold as
we'll in Allegheny with gases made in Pitts
burg as is done now in Dimling's restau-
rant, and is very enthusiastic over the pos
'ibility of doing better work than he has
been able to do with ice in the way of cold
storage.
In lecture before the Society of Arts
Boston, some of the drawbacks to the use
of aluminium were set forth by A. E. Hunt
The pure metal, he said, is softer and weaker
han the commercial variety containing 8 to
per cent of impuritv, and the tendency of
The metal to become coated with thin film