There must be some such unsusceptible substances in nature.

Radium does not seemingly manifest itself when distributed through pitchblende; and there are doubtless other such substances in which it can be imprisoned.

Possibly these may belong to that class of "inert" elements discovered or isolated by Sir William Ramsay.

It is therefore possible that in this Coffer, made from an aerolite and therefore perhaps containing some element unknown in our world, may be imprisoned some mighty power which is to be released on its opening." This appeared to be an end of this branch of the subject; but as he still kept the fixed look of one who is engaged in a theme we all waited in silence.

After a pause he went on: "There is one thing which has up to now, I confess, puzzled me.