key is raised up
so that its rear end strikes the screw head J. This action of the key is
instantly duplicated by the bar D (Fig. 68) of the sounder, so that the
sounder as well as the receiver knows the time between the first and the
second click, and by that means he learns that a dot or a dash is made.

ILLUSTRATING THE DOT AND THE DASH.--To illustrate: Let us suppose, for
convenience, that the downward movement of the lever in the key, and the
bar in the sounder, make a sharp click, and the return of the lever and
bar make a dull click. In this case the ear, after a little practice,
can learn readily how to distinguish the number of downward impulses
that have been given to the key.

_The Morse Telegraph Code_

A . - N - . & . ...
B - ... O .. 1 . - - .
C .. . P ..... 2 .. - ..
D - . . Q .. - . 3 ... - .
E . R . .. 4 .... -
F . - . S ... 5 - - -
G - - . T - 6 ......
H .... U .. - 7 - - ..
I .. V ... - 8 - ....
J - . - . W . - - 9 - .. -
K - . - X . - .. 0 ---- ------
L -- Y .. ..
M - - Z ... .

EXAMPLE IN USE.--Let us take an example in the word "electrical."

E L E C T R I C A L
. -- . .. . - . .. .. .. . . - --

The operator first makes a dot, which means a sharp and a dull click
close together; there is then a brief interval, then a lapse, after
which there is a sharp click, followed, after a comparatively longer
interval, with the dull click. Now a dash by itself may be an L, a T, or
the figure 0, dependent upon its length. The short dash is T, and the
longest dash the figure 0. The operator will soon learn whether it is
either of these or the letter L, which is intermediate in length.

In time the sender as well as receiver will give a uniform length to the
dash impulse, so that it may be readily distinguished. In the same way,
we find that R, which is indicated by a dot, is followed, after a short
interval, by two dots. This might readily be mistaken for the single dot
for E and the two dots for I, were it not that the time element in R is
not as long between the first and second dots, as it ordinarily is
between the single dot of E when followed by the two dots of I.

CHAPTER X

HIGH TENSION APPARATUS, CONDENSERS, ETC.

INDUCTION.--One of the most remarkable things in electricity is the
action of induction--that