Moreover, the entire print was covered by a network of fine black lines, by which it was divided into a multitude of small squares, each square being distinguished by a number.
"Excellent, Polton," said Thorndyke approvingly; "a most admirable enlargement.

You see, Jervis, we have photographed the thumb-print in contact with a numbered micrometer divided into square twelfths of an inch.

The magnification is eight diameters, so that the squares are here each two-thirds of an inch in diameter.

I have a number of these micrometers of different scales, and I find them invaluable in examining cheques, doubtful signatures and such like.

I see you have packed up the camera and the microscope, Polton; have you put in the micrometer ?" "Yes, sir," replied Polton, "and the six-inch objective and the low-power eye-piece.