gradually from those same tanks. This was the means by which the
submarine boat rose to the surface. All the time that he was doing this,
Jack Benson kept his keen glance on the submersion gauge. At last he
stopped.

"How is it up there, Eph?" he called, pleasantly.

"Why, of course there's a lot of good daylight filtering down through the
water now," Somers admitted.

Captain Jack went nimbly up the spiral stairway. Now, he had still
another piece of apparatus to call into play. This affair is known to
naval men as the periscope.

In effect, the periscope is a device which in the main is like a pipe;
it can be pushed up through the top of the conning tower, through a
special, water-proof cylinder, until the top of the periscope is a foot,
or less, above the surface of the water.

The top of this instrument is fitted with lenses and mirrors. Down
through the shaft of the periscope are other mirrors, which pass along
any image reflected on the uppermost mirror of all. At the bottom of
the periscope is the last mirror of the series, and, opening in upon
this, there is an eyepiece fitted with a lens.

As Captain Jack Benson applied his right eye to the eyepiece he was able
to see anything above the surface of the water that lay in any direction
that the periscope was pointing.

"Right opposite Spruce Beach, as the chart showed!" chuckled the young