ce between the spark current and the spark light as to which
arrives first. The current jumps just before the spark appears; so it
is possible for the current to reach the camera and close the shutter
even before the light which is to be pictured arrives.

By lengthening the wires between the spark gap and the camera the
light is allowed to arrive first. By suitable adjustment of the
wiring, the shutter can be made to close during any one-billionth of a
second interval during the first four ten-millionths of a second of
the spark's short life.

The camera shutter consists of two Nicol prisms of Iceland spar and
balsam, arranged in such a way that under ordinary conditions the
light coming from the spark is stopped by polarization and prevented
from reaching the camera. Between these two prisms, however, is a
solution of chemicals which will depolarize the light and allow it to
continue.

The wires leading from the spark gap connect with this solution. When
the current jumps across the gap it races down the corridor and
electrifies the solution for about one-billionth of a second. This
electrification removes the depolarizing effects of the solution and
light passage stops; in other words, the shutter is closed.

The Diamond Thunderbolt

_By H. Thompson Rich_

[Illustration: "_Good Lord! What's this?_"]

[Sidenote: Locked in a rocket and fired into space!--such was the fate
which awaited young Stoddard at the end of the diamond trail!]

Prof. Norman Prescott, leader of the American Kinchinjunga expedition,
crept from his dog-tent perched eerily at the 26,000-foot level of
this unscaled Himalayan peak, the third highest in the world. With
anxious eyes he searched the appalling slopes that lifted another
2,000 feet to its majestic summit, now glistening in the radiance of
sunset.

Where was young Jack Stoddard, official geologist and crack
mountaineer of the party?

That morning Professor Prescott and Stoddard had set off together,
from Camp No. 4, at the 22,000-foot level. Mounting laboriously but
swiftly, they had reached the present eyrie by noon. There Stoddard
had left the leader of the expedition and pushed on alone, to
reconnoiter a razor-back ridge that looked as though it might prove
the key to the summit.

But the afternoon had passed; the daring young geologist had promised
to return in an hour; and now it was sunset, with still no sign of
him.

Professor Prescott sighed, and a bitter ex