The San Francisco call. [volume] (San Francisco [Calif.]) 1895-1913, 1895-03-17

"A most interesting
and valuable method of annealing armor
plate Is described by Professor Elihu
Thomson. In this method electricity is
used for producing a local softening of the
surface of the plate. Proiectiles are now
hurledwith such terrific force from rapid fir
ing guns that ordinary armor plate, exposed
to their fire, would be quickly perforated,
smashed and destroyed. The plate has to
be given a surface of superior resisting
power, and for this purpose it is subjected
to the process of "Harveyizing" that is,
it is provided with a skin of hard steel of
greater or less thickness. This is effected
by keeping the plate hot in contact
with carbon. The carbon then enters the
face of the metal and so enriches it that
by a subsequent operation in which the plate
Is rapidly chilled it acquires the properties
of very hard steel. When struck by a pro-
jectile this hardened surface repels the i'm
pact SO effectively that the puncturing end
of the shot is broken up and its entrance
into the body of the plate which, behind
the Harveyized surface, is of soft material
is prevented. The thickness of this chilled
and hardened coating may vary from
half to three-quarters of an inch. 1t is pos
sible while passing the plate through this
process to exempt certain portions from
carbonization, but there has always been
difficulty In confining the exempted area
accurately, and parts might be left soft
which should be hard, and vice versa. The
real object OF annealing, or softening, the
spots on the armor plate, is of course to
enable holes to be drilled through the sur
face and screw threads to be cut into them
by tapping, SO that the plates themselves
can be attached or have parts of the ship
attached to them. Various means of doing
this have been attempted, especially the
application to the surface of the plate of
the intense heat OF the oxyhydrogen blow
pipe, but all have failed. The electric pro-
cess, which is now used successfully, con-
sistS in heating portion of the plate to an
annealing temperature by passing cur
rent between two electrodes placed at
certain distance apart on the plate surface,
and then by diminishing the current, low
ering the temperature so slowly that the
massive plate at the back cannot cause
a chill on the heated portion of the metal.
In other words the application of heat is
so regulated that the temperature at the
heated or appealed spot is maintained in
definitely or changed so gradually that the
subsequent hardening, which would ordi-
narily be the effect of a sudden chill, is
prevented. The case of the warship Mas
sachusetts, now under construction, in
which it is found that certain of the ar
mored plates for the barbettes possessed
the toughened Harveyized skin in places
where it was absolutely necessary that they
should be drilled and tapped, showed very
clearly the value of the process. Blow
pipes had been tried in vain and the build
ing of the ship was at a standstill. The
application of the electric annealing pro-
cess put an end to the difficulty and the
work of construction was at once renewed.
REPRODUCING BASEBALL GAMES BY ELEc-
TRIcITY.-There have been many i'm
provements in the reporting of dis
tant baseball games for the benefit
of persons who, unable to escape
from the claims of business within the
city, are yet SO full of enthusiasm for the
game that they steal away to the nearest
newspaper Office where tally of the score
in progress is being kept. Some of these
Improvements reproduce the leading feat
ures of the game SO graphically as to add
greatly to the interest and excitement of
the large number of spectators they in
variably draw; but in completeness and
effectiveness a new system, worked cleo
trically, eclipses them all On a large
sheet is portrayed the ball ground in front
of crowded stand, and the pictures of the
players are painted at the respective posi-
tons occupied by the side that is in the