58 
TRANSACTION'S OF THE TEXAS ACADEMY OF SCIENCE. 
F 
o 
B 
D 
squares (A and B)of sheet zinc 16 c.m. on theside,each provided with a rod 
(C and D), terminating in a hall (E and F). The 
two plates were set up in the same vertical plane, 
with the knobs almost in contact. To the rods were 
attached the terminals of a large Buhmkorff coil. The instrument used 
to detect the radiations from the sparks passing between the knobs was 
called a resonator, and consisted of nothing more than a single wire of 
about 2.2 meters in length, bent into a circle, and having its free ends 
terminating in small knobs, whose distance apart was varied by a microm- 
eter screw. When this resonator was held near thp vibrator, sparks in the 
former would produce a corresponding sparking in the latter, though of 
such diminished intensity as usually to be visible only in a darkened 
room. By holding the resonator in various planes and bringing the spark 
gap into different positions, he was enabled to show that this radiation 
was made up of two components, the one electric, the other magnetic. 
The experiment by which he clearly proved that this radiation has a 
finite velocity, and by which also it is generally supposed that he proved 
this velocity to be the same as that of light, was as follows: The vibrator 
had been placed in one end of a room about 15 meters in length, and the 
resonator had responded to its action to the full length of the room. But 
when a large metal screen was placed at the opposite end of the room 
certain positions Avere found Avhere the sparking of the resonator was 
greatly diminished or entirely extinguished. Beginning near the screen 
with a well-defined spark, the resonator was carried towards the vibrator. 
Before the introduction of the screen this approach was always accom- 
panied by increased brilliancy in the resonator spark; but now it had an 
opposite effect. At a certain distance in front of the screen the spark 
was almost extinguished. But beyond that point it began to increase, and 
at a greater distance regained its former brilliancy. Further on it again 
diminished, to be revived at a still greater distance. These two positions 
of minimum sparking were at about successively equal distances from the 
screen. The most natural explanation of this was that these positions of 
minimum effect were nodal points, produced by the interference of the 
direct and reflected waves. According to this view the distance between 
these points was the measure of a half wave length. The period of oscil- 
lation was calculated by the well known formula T = n ^LC, and was 
found by Hertz to be 1.4 hundred-millionth of a second. Multiplying 
the half wave length by the reciprocal of the time gave 320,000 k.m. for 
the velocity, approximately thai of light; and, therefore, the same ether 
was the medium of both. 
It has already been stated that in attempting to repeat this celebrated 
experiment I obtained a very different wave length from that found by 
