given up to chemical research, as was shown by the shelves of
reagents that covered the wall, and the flasks, retorts and other
apparatus that were arranged on the bench, like ornaments on a
drawing-room mantelpiece. On the opposite side of the room was a large,
massively-constructed copying camera, the front of which, carrying the
lens, was fixed, and an easel or copyholder travelled on parallel guides
towards, or away, from it, on a long stand.

This apparatus Thorndyke proceeded to explain to our visitors while
Polton was fixing the "Thumbograph" in a holder attached to the easel.

"You see," he said, in answer to a question from Miss Gibson, "I have a
good deal to do with signatures, cheques and disputed documents of
various kinds. Now a skilled eye, aided by a pocket-lens, can make out
very minute details on a cheque or bank-note; but it is not possible to
lend one's skilled eye to a judge or juryman, so that it is often very
convenient to be able to hand them a photograph in which the
magnification is already done, which they can compare with the original.
Small things, when magnified, develop quite unexpected characters; for
instance, you have handled a good many postage stamps, I suppose, but
have you ever noticed the little white spots in the upper corner of a
penny stamp, or even the difference in the foliage on the two sides of
the wreath?"

Miss Gibson admitted that she had not.

"Very few people have, I suppose, excepting stamp-collectors," continued
Thorndyke; "but now just glance at this and you will find these
unnoticed details forced upon your attention." As he spoke, he handed
her a photograph, which he had taken from a drawer, showing a penny
stamp enlarged to a length of eight inches.

While the ladies were marvelling over this production, Polton proceeded
with his work. The "Thumbograph" having been fixed in position, the
light from a powerful incandescent gas lamp, fitted with a parabolic
reflector, was concentrated on it, and the camera racked out to its
proper distance.

"What are those figures intended to show?" inquired Miss Gibson,
indicating the graduation on the side of one of the guides.

"They show the amount of magnification or reduction," Thorndyke
explained. "When the pointer is opposite 0, the photograph is the same
size as the object photographed; when it points to, say, x 4, the
photograph will be four times the width and length of the object, while
if it should point to, say