th
the reflection and refraction of rays of light, will understand how an
ingenious contrivance produced the results spoken of. The same principle
enters into the arrangement of the _camera obscura_. There was an aperture
very artfully cut through the wall, and so guarded on the outside as to
escape notice; and in this a tube was placed with a set of happily
contrived fixtures, by the aid of which the scene without was accurately
depicted on the polished surface within. It was the work of the captain, as
Eveline supposed.

As this contrivance was evidently intended to give information of danger
from without, it must certainly be connected in some manner with the means
of escape; else what was it worth? Such was the conclusion to which Eveline
arrived, as she philosophized upon the matter. And she reflected further,
what other method of escape was there, save a secret medium of
communication with the outer world? None at all, except it be a quiet
waiting within the passage she now herself occupied, which she could not
bring herself to believe was the case; so she renewed her search for the
door of egress.

On minutely examining the mirror, she saw at one side of it a small
projection, like a ball of ivory, and pressing hard upon it, a door, of
which the mirror itself was a section, sprang a little way open. She threw
it back wide on its hinges, and holding her lamp in the opening, saw at her
feet a flight of stairs leading down into the gloom below. A damp current
of air came up from this subterranean cavity, and its clammy coldness sent
a chill almost of horror through the frame of the agitated girl. One less
resolute than herself would have shrunk at the idea of exploring so dismal
a looking place; but not so she. Summoning all her energy, she boldly
descended the steps, which had evidently been cut out by the hands of man,
and soon found herself at the bottom of the course. In front of her, all
was solid earth and rock; but on turning to the right she discovered an
opening, following which it was but a little while till she saw light
ahead, and a few more steps brought her to the margin of the stream, along
the bank of which was the path to the cave. That path, then, was
immediately above her! And here she was with the wide world before her! How
her heart bounded!

Her first thought was to fly immediately; but prudence dictated a cautious
survey of the place before venturing her all in an attempt at flight.

She a