come to any
rational conclusion. The distressing effect of the light rays increased,
rather than diminished, as his nerves became more and more unstrung. It
seemed, even with, his eyes closed, that he could feel the _weight_ of
the cone of light upon his face. The desire to escape from its searching
glare became well-nigh irresistible. How long would this torture
continue? He began to feel intensely tired and worn out and realized
that could he but shut out the blinding brilliancy which enveloped him,
he would sink exhausted to sleep. Sleep! He could no more sleep, under
the present conditions, than he could fly to the moon. Then there came
to his mind a recollection of a form of torture practised among the
Chinese, the prevention of sleep. Prisoners, he had read, were confined
in a cage, in brilliant sunlight, and prevented from sleeping by being
prodded from without with spears. At the expiration of a week, he had
read, the victim goes raving mad. Was this, then, Hartmann's intention?

Whatever the man did, he knew he would adopt only such methods as would
involve him in no damaging consequences. He might be kept in his present
situation until insanity ensued, and Hartmann with his reputation as a
physician, a scientist, could calmly deny any story he might tell,
putting it down to the wanderings of a disordered brain. He realized the
cunning of the man, his care to use no physical violence. Should he,
Duvall, under the strain of the torture which he realized lay before
him, consent to disclose the whereabouts of the ivory snuff box, in
return for his liberty, what could he do, in retaliation? Hartmann would
calmly deny his story, and would doubtless produce witnesses, such as
Mayer, to prove that the detective came to him for treatment for some
slight mental disorder, some lapse of memory and that the exposure to
the light rays had been but part of his usual treatment. Clearly the
doctor had covered his tracks most successfully.

Throughout all these torturing thoughts, the figure of Grace came and
went unceasingly. What would she do--what could she do, to aid him? He
had warned her not to ask Mr. Phelps to take any steps looking to his
release. He realized that were Hartmann to appear now, and give him his
freedom, he would not dare to accept it. That the doctor might do this
very thing was his greatest fear. If he should insist upon his leaving
the place, what could he do, then, to recover Monsieur de Grissac's
s