through
all the known geological strata in that part of New Jersey, and had
reached subterranean depths known to Clewe only by comparison and
theory.

The apparent excavation had extended itself down so far that the disk
at the bottom, although so brightly illuminated, was no longer clearly
visible to the naked eye, and was rapidly decreasing in size on account
of the perspective. But the telescopes which Clewe had provided easily
overcame this difficulty. He was sure that it would be impossible
for his light to penetrate to a depth which could not be made clearly
visible by his telescopes.

It was a wonderful and weird sensation which came over those who stood,
glass in hand, and gazed down the track of the Artesian ray. Far, far
below them they saw that illuminated disk which revealed the character
of the stratum which the light had reached. And yet they could not see
the telescope which they held in their hands; they could not see their
hands; they knew that their heads and shoulders were invisible. All
observers except Clewe kept well back from the edge of the frightful
hole of light down which they peered; and once, when the weight of the
telescope which she held had caused Margaret to make an involuntary step
forward, she gave a fearful scream, for she was sure she was going to
fall into the bowels of the earth. Clewe, who stood always near by, with
his hand upon the lever which controlled the ray, instantly shut off
the light; and although Margaret was thus convinced that she stood upon
commonplace ground, she came from within the screen, and did not for
some time recover from the nervous shock occasioned by this accident of
the imagination.

Clewe himself took great pleasure in making experiments connected with
the relation of the observer to the action of the Artesian ray. For
instance, he found that when standing and gazing down into the great
photic perforation below him, he could see into it quite as well when he
shut his eyes as when they were open; the light passing through his head
made his eyelids invisible. He stood in the very centre of the circle of
light and looked down through himself.

That this application of light which he had discovered would be of the
greatest possible service in surgery, Roland Clewe well knew. By totally
eliminating from view any portion of the human body so as to expose a
section of said body which it was desirable to examine, the interior
structure of a patient could b