, / 4, the photograph will be one-fourth the
length of the object. It is now, you see, pointing to x 8, so the
photograph will be eight times the diameter of the original thumb-mark."

By this time Polton had brought the camera to an accurate focus and,
when we had all been gratified by a glimpse of the enlarged image on the
focussing screen, we withdrew to a smaller room which was devoted to
bacteriology and microscopical research, while the exposure was made and
the plate developed. Here, after an interval, we were joined by Polton,
who bore with infinite tenderness the dripping negative on which could
be seen the grotesque transparency of a colossal thumb-mark.

This Thorndyke scrutinised eagerly, and having pronounced it
satisfactory, informed Mrs. Hornby that the object of her visit was
attained, and thanked her for the trouble she had taken.

"I am very glad we came," said Miss Gibson to me, as a little later we
walked slowly up Mitre Court in the wake of Mrs. Hornby and Thorndyke;
"and I am glad to have seen these wonderful instruments, too. It has
made me realise that something is being done and that Dr. Thorndyke
really has some object in view. It has really encouraged me immensely."

"And very properly so," I replied. "I, too, although I really know
nothing of what my colleague is doing, feel very strongly that he would
not take all this trouble and give up so much valuable time if he had
not some very definite purpose and some substantial reasons for taking
a hopeful view."

"Thank you for saying that," she rejoined warmly; "and you will let me
have a crumb of comfort when you can, won't you?" She looked in my face
so wistfully as she made this appeal that I was quite moved; and,
indeed, I am not sure that my state of mind at that moment did not fully
justify my colleague's reticence towards me.

However, I, fortunately, had nothing to tell, and so, when we emerged
into Fleet Street to find Mrs. Hornby already ensconced in a hansom, I
could only promise, as I grasped the hand that she offered to me, to see
her again at the earliest opportunity--a promise which my inner
consciousness assured me would be strictly fulfilled.

"You seem to be on quite confidential terms with our fair friend,"
Thorndyke remarked, as we strolled back towards his chambers. "You are
an insinuating dog, Jervis."

"She is very frank and easy to get on with," I replied.

"Yes. A good girl and a clever girl, and comely to look u