Page:The Master of Mysteries (1912).djvu/167

 into the studio, unable any longer to control her curiosity.

Astro drew out the evidence in the case and spread it before her. "All life is made up of trivial actions," he began. "Every one of them leaves its little trace. Whether you are tracking a bear by its footprints through the forest, or a criminal through his nefarious deeds, it is the same thing. Both leave their spoor behind. Now examine this letter and envelope carefully."

Valeska took the magnifying-glass and scrutinized both; but was forced to acknowledge her defeat.

Astro took the envelope from her and tilted it to the light. "Do you see a slight mark there?" he asked. "It is the print of a thumb. It is not generally known that a finger pressed on paper will leave an invisible oily impression, especially when the hand has recently been passed through the hair. So it will on glass or any polished surface. Let us develop this print. The ink will cling to the paper except where these oily lines have been in contact with it. An ordinary thumb print would show the lines of the ridges; this will show those of the channels between the ridges."

Dipping a large brush in ink, he swept it lightly over the paper. The ink flowed away from a patch where a little system of concentric lines appeared.

"Lo! the invaded loop!" he announced. "It is a woman's thumb. I saw it yesterday, and copied its fundamental diagram and its core. Now look at the mucilage on the flap. Do you see those tiny grains? Snuff, as I proved by my microscope. The postage-stamp is awry, and half off, and also shows tiny traces of snuff. The woman was in a hurry. The corners