The Salt Lake herald. [volume] (Salt Lake City [Utah]) 1870-1909, 1897-12-12

laws of nature they show that patience
and determination can overcome al
most all difficulties-and this is quite
enough for the latter.
If we throw a stone into a pool of
water we produce q series Of motions
on its surface which go by the name Of
waves, rippleS or fluctuations, and we
experience no difficulty in seeing these
waves with the naked eve because their
length is comparatively large. Scien-
fists determine the length OF wave
motion (whether in the air the ether,
the sea, or in any liquid surface) by
measuring the distance between crest
and crest. The length Of & wave is, in
fact, the distance from crest TO crest.
Now it is quite possible to produce lit
tie waves or nipples On d liquid surface
which are so small, which follow each
other With such great frequency. and
which pass SO quickly before the eye
as TO be perfectly invisible.
Those Who have attended scientific
lectures, Of course, know the means
taken TO render visible these ordinarily
invisible little waves. They are shown
either by what is known as the "stro-
hoscopic method" or else by the pro-
6uction of an instantaneous light. The
first method has often been shown at
public lectures by Professor c. V. Boys,
and is as follows.
OLD AND NEW METHODS.
A water surface focused on the
screen appears unaffected by being
touched with the point Of a feebly
sounding tuning fork Directly, how
ever. the light is intercepted with
revolving disk. rotating in time with
the fork. the ripples are seen clearly
enough through the opening of the
disk This method is akin to the in
Simultaneous shutter employed by the
photographer or the cinehet0graph-
err" and has been used with great eff
feet by Professor Maybridge in his
photographs Of trotting horses, etc. 1t
viii a. once be seen that it comes to
the same thing whether we look at the
ripples by al instantaneous light or
whether we use some mechanical de-
vice and allow the ripples to be sub
mitted 90 brief periods Of light. IN
Simultaneous Photography" is not quite
a defensible term, because no pho
Biography can be really instantaneous,
but the time taken IS 50 extremely mi
mute that the phrase may be allowed
to pass. We can employ either the
magnesium ilashlight-W which varies
from one-tenth to cne-fifteenth OF a
Second-or we may use the electric
spark. Professor Rood Of New York
some time back made some expert
ments on the duration of the discharge
of a Leyden Jar. and also on tnat o.
lightning, and he proved that IN certain
cases the duration OF an electric spark
across the knobs OF Levden lars
charged from a Wimshurst machine
was as short as one twenty-five mil
liontb part of q second of timel
Now. in order 20 bring home the fun
force OF this statement. let me borrow
an illustratio ] once heard Lord Ray
leigh use. 4 million seconds is about
i days and nights; %, 900. 900 seconds is
nearly a year-so that the time occu-
pied by the spark in Professor R0od's
experiment is about the same fraction
Of one second that enc second is of a
year.
Mr.. Vincent attains his results by
the sudden illumination OF an electric
spark. The spark is about half a cen
timeter in length and II lasts about the
one two hundred JhOgsandth part Of a
second Not So short ii period as one
Twenty-Five millionth part OF a second.
which it viii be remembered WAS the
time of the spark employed by Profess
soP Rood, but nevertheless an incred-
ibly short period. To determine the
duration of such a spark (Which may
be said TO have scarcely any being at
all for it dies as soon as it is born). is
a difficult task. The scientist has re-
course to that wonderful weapon. the
revolving mirror, first employed by
Mheatscone, and since used TO deter
mine the velocity OF light
MI. Vincent uses o second spark (pro-
duced in the usual way by connecting
q Wimshurst machine with the knobs