The Irish standard., 1899-02-04

W uuu lue law u IceletNuCe III SLlll dlF.
Moreover, the blast would defect the
light bullets so much that they could not
be made to strike a target, and so the
chronograph would not record their We
locity. Thus, all things considered, the
odd-looking cannon is very aptly and
simply designed for its purpose.
The hollow bullets used in this inves-
tigation are difficult to make with per-
feet nicely. At first hollow wooden
ones We're used but they warp percept-
IDLY and break after few flights, even
though the target is barrel of soft cot
ton. variety of plans was offered
for producing hollow balls easily. Glass
balls, rubber balls, plaster of paris
balls, cocoanuts, gourds, were suggested.
1t was mischievously intimated that
large eggs might be used. but the inven-
tor replied that, even If he had bird to
lay IA steel eggs, 1t is doubtful if they
would be accurate to one-thousandth of
an inch, as the measurement requires
So finally it was found best to stamp
hemispherical shells out of sheet steel,
and solder them into hollow spheres.
These are sufficiently strong to give per-
fectly good results, and the same ball
may be used over again many times,
since the cotton target catches 1t with
out injury.
But the most remarkable instrument
of ho ot,,c ic oh
graph. This had to be so designed as to
offer no resistance to the bullet, and yet
measure the time of it's arrival at three
points-of Its path as it flies from the
guns muzzle to the target. The time Of
arrival at these points mad to be meas
ured accurately to one-mililonth part Of
a second. The first instrument invented
for this purpose gave exactly the re-
quired precision. and now DR.. Zahm af-
firms that he has invented another in
strument that will measure a hundred
milliOnth of second. These are cer-
tainly the most accurate time records
known to science. Fortunately, too,
they are applicable to a very general
variety OF phenomena in physical sci
ence-from electric discharges to horse
racing.
His chronograph is as simple as it is
accurate. To conceive its main features
one must picture three thin streams of
light shining squarely across the bullets
path; one near the guns muzzle, the
others at intervals of several yards.
After crossing the bullets path, the PEN
ellis of light strike oblique'mirrors which
defect them and make them all pass
into one pin hole In cast-iron box, in
side of which is a Photographic plate
moving rapidly. The three pencils of
light touching the sensitive plate in
sharp focus. trace three fine black lines,
each of which is momentarily interrupt
ed when the bullet outs It's tracing sun
beam. The plate is then developed, and
the distances between the Interruptions
in the tracings are measured under a
microscope From these measurements
the velocity and resistance of the bullet
are easily calculated. The castings for
this interesting cannon have been sent
to Washington, where Prof. Zahm is ar
ranging to have them bound and COM
pleted at the gun works of the navy
yard. The gun will then be Installed in
one Of the large laboratories of the Cath
olic University, in place of the one hith-
erto used In his experiments, and with
which he has discovered the law of at
mospheric resistance for considerable
! range of velocities. With the new gun
the law of resistance will be determined
for all velocities, from the lowest to the
highest, that can be obtained.
Besides the purely physical interest in
ascertaining the law of atmospheric
resistance, DR.. Zahm is especially at
tracted by It's bearings on aerial navi-
cation, branch Of science in which he
mas always been Interested, and in
which he has accomplished some valua-
Die work. He was secretary for the in
ternational conference on aerial naviga-
ton in 1893. In fact. it was mainly
| through his efforts and those of Mr..
Chanute, of Chicago. that the conference
| was organized and carried to a success
| full issue. He is the inventor of MANY
! other interesting devices in physical sci
, ence, one of which is to be used in
naval warfare, and has received the
commentator of the navy department,
Dr.. Albert f. Zahm is younger
| brother Of the Very Rev. DR.. Zahm. c.,
S. c. The tastes of the two brothers are
in many respects the same, and much of
| their work has been along the same
lines. For this reason one has often
been mistaken for the other. DR.. Az
bert Zahm has written considerably for
the press, and is. we understand, soon
to publish In book form the results of
MS remarkable Investigations on at
mospheric resistance, most of which
were carried on in the we'll equipped
laboratories of the Catholic University
of America.
| Bobby lat the breakfast tablet e)-Maud,
did Mr.. Jules take any of the umbrellas