The daily morning journal and courier. [volume] (New Haven, Conn.) 1894-1907, 1896-03-04
CATHODE RAYS EXPLAINED
PROFESSOE 4. ". WRIGHq'S INTER
ESTING LECTURE List EYENING.


Eighth in the Mechanics Course History
of the Cathode Rays-Early Experiments
Beautiful Light Enects-Methods EN-
ployeh-How Pictures Are Taken-Inter-
esting Pictures of Experiments Shown
Large Audience.
The eighth and probably the most i'll
teresting thus far in the Mechanics
course of lectures was delivered at
North Sheffield hall by Prof. A. W.
Wright oe Yale on Cathode Rays"
Prof. Wright has recently become prom
inent as an experimenter with the new
discovery and has made many valuable
experiments. The lecture room last
evening was literally packed, every
available foot of standing room being
occupied for half an hour before the
lecture began. At s o'clock the crowd
continually pouring in was so great that
minutes the doors opening into the hall
were opened and the corridor was soon
full of chairs, on which were standing
persons eager to catch the speakers
words and see the experiments, while
the stairway was lined with spectators
The outside doors were kept locked.
Prof. Wright said seldom are scientists
called upon to investigate a greater
question than the one of the cath
ode rays. For years efforts have
been made to find out the principle, but
| 1t had at last come to be thought that
such principle was non-existent, when
suddenly with flash the new discovery
was made. The first step to take in
| tracing this discovery is the considera-
| tion of the simple electric spark Prof.
| Wright then adjusted his apparatus and
| proceeded to show the electric spark,
and continuing said: ''The spark is
very similar to lightning. Now when
l connect these wires with the platinum
ends of this closed tube a wonderful
change is shown. instead of single
spark, a long stream of light is seen,
blue at one end-blue is always seen at
the negative end, and this is called the
cathode end. The other end is called
the anode. because the current enters
| blItiC. llt. illllOSpISIt III lilc tuDC
| which I have just used is about one
half density. Now l take a tube with
only 1-90 density of air, and another
change is seen. The light is greatly in
creased, and the blue end is more dis
| tinct. Now take one of the Geissler
tubes with only milimeter and one
half density of air and another change
takes place. The blue end is entirely
| isolated from the rest, and the positive
end glows with pinkish color. Crooke
made a great advance over Geissler.
| While the general luminosity of his
| tubes is less than that in Geissler's, the
| f1oresence is greatly increased. 1t is
with these tubes that Prof. Bunstead
and myself have made our experiments.
! Placing different florescent materials
| in these tubes different colors are given
off, sometimes blue, sometimes purple
| and again yellow. 1t seems as if the
materials gave off the colors themselves
and in fact that is the case, the
cathode rays having that effect on
| them.
Now I will explain the way in which
we take the photographs which aIe so
much talked of to-day In the first
| place the plate has to be well protected.
| This can be done by means of the or
dinary plate holder, which is covered
with metal about one-haf inch in
thickness. The object 10 he pnoto-
graphed is laid on the plaIa holder and
the Crooke's tube is placed six Or eight
| inches above it. The electric current is
then turned on and the negative eX"
1 posed for sufficient length of time.
| The time varies according 70 the dem
sity of the substance through which
the rays are to pass and also accord
| ing to the kind of tube used
| We have seen from some Of the ey-
periments that the rays escape to the
outside of the tube. Leaard Of Baum,
Germany. first discovered that the es-
cape of these rays would be facilitated
| by inserting a piece of aluminium in
the Croolze's tube. He discovered this
about two years ago and while making
some further experiments to find the
relative transparency of aluminium and
quartz to the cathode rave he made
| the first picture with the rays which
was ever made. This picture he made
through a covered box, in which he
| had inserted the substances with which
he was experimenting We see frcln
! ILLS tlldL ieotHlScu was ilOt THE IlTSI 70
| make picture with the rays, but his
! discovery is none the less valaa Die,
| Lenard hardly realized what Il prirci-
| pie he had found and did not follow it
out. His work merely proved that
cathode rays could penetrate through
the tube into surrounding space for
a few inches, while Roentgen has shown
| that they can be made to pass through
| several feet. His discovery was made
| in following up the train of expert
ments that Lenard began. He was
| trying to find at the time by means
of the cathode rays, whether waves
of ether were longitudinal In these
experiments he discovered the fact
which has aroused such interest in
| scientific circles recently, that rays of
! light can be made to penetrate opaque
| substances"
| Professor Wright illustrated his talk
at every point with apparatus and
showed how by having the air in the
! tubes at different densities varying
shades of color We're produced. He all
so illustrated the method of taking pic
lures by the rays. Some of the exueri-
ments produced most beautiful light
| effects, especially one, in which two
rubies were placed III the tube. The
/ glass of the tube produced a green tint
while the bright red of the ruby was