The sun. [volume] (New York [N.Y.]) 1833-1916, 1897-09-19

Photographers In the One Hundred Thousandth
Part or y Second.
Prom the ntt,burp Dtspatch.

From the Pfftsburp Dtspatch.
The new photochronograph. designed for the
United States Government to test the velocity
of cannon balls. will be completed by Prof. John
A. Brashear At his Allegheny workshops to-
morrow. George Squire. Lieut. nant OF Art!l-
lery at Fortress Monroe, will arrive in Pitts
burg tomorrow to inspect the new apparatus.
The new machine is the second one made for the
Government by Prof. Brashear and has many
valuable Improvements over the first one. al.
though the main principles have not been
changed. Lieut.. Squire and DR.. Crehore. one of
the inventors. have severely tested the wonder
ful apparatus, and it has met all the expecta.
tions Of I e Government experts. II is very
s' m he but mrs . is pos s5 e @, great S~t on eu rinSy: lava.
is used to fir" the gun, to start the tuning fork
to, %vihrate. to open the main shutter. and also 70
release the electric connections which throw tho
IS. as soon as the lever is pu{ed the cannon MS /;
opens the way TO the photorraphic plate. which
is rotating l.5oo revolutions per. minute. A
Ss6srS t Of % Rhish 0 is f deie rhGinSsaFqSg y the pl rseid tie
at which the pail C cuts ST the second &C y wire, where II
As this distance can be readily measured the
question is to determine how long the bal is
strikes the frs. wire in front OF the cannon
tuning fork is set in vibration. and through .
ef''s ,ss pPenins Of n the I s" tnni aasP forfF a p po 9n.
full beam OF light is sent on 10 the Mo
Geographic plate; The vibrations OF the Tn.
makes a sinuous stream Of light a~loAgsirs
OF the. streak produced by the moving can.
non ball it is only a question OF measuring ;hs
vibration OF the tuning fork covere1 by tbs
streak. rs also the fractions OF a vibration. In
measuring the fractions of the vibrations Of a
tuning. fork is where the most delicate work
comes in.
After the Photographic plate is developed 1t 10
placed under a divided circle and the relations
OF the two photographic streaks measured
with q micrometcr. So exact has this method
been found th1t the movement of a ball two or
three inches can readily he timed.
Hereafter mea OF such short inter.
walls have been impossible. for the reason that
no Photographic shutter that had weight cold
be moved in such a brief spsce OF time, and u
Instead of moving something that has msss
on two Nieols prisms which lie al risht
/ impossible for light to pass through at
Al. and It was DIR. Crehore who discovered that
IL powerful current Of electricity be posset
prisms the light itself can he rotated without
rotating the prisms. II can be readily seen that
trio current hns no weight it can be moved in an
incredibibly short space OF time. And even with
the lag that accompanies all motion any view
lasting over the one hundred thousandth part
OF q second can be photographed.
The instrument made last year proved 40
valuable at Fortress Monroe that the new ma.
ground. Not only can the velocity OF cannon
balls be determined between any two points
outside the Commons mouth, but 1t can be meas
nred within the cannon. Formerly any attempt!
In this direction were rather unsuccessful. md
the way IL WAS done was quite destructive TO The
gun: as : foot at a time was cut OF from he end
Is only necessary now to, place a stout wooden
ramrod AGAINST the bal place copper rings
around the Pamrod. and make connection with
these rings by electric brushes at the muzzle Of
the gun.