pretty woman; evidently the same model in each instance, though used in connection with different products. In one pose the girl held a loaf of bread in her hand; in the other she displayed her gleaming teeth whitened by "Dentabella," a new proprietary toothpaste. She was pretty and quite young. Next was a card, curiously covered with an intricate series of interlaced curves in purple ink,—a beautiful, symmetrical pattern, as accurately drawn as the lathe engraving on a bank-note. Last, there was a small printed page containing a calendar with all the months given. Oddly enough, the year was not printed at the top; instead, above the calendar proper appeared the caption, "Number fourteen."
Valeska looked at the collection curiously. "Well," she said at last, "I can't make much of anything except the girl's picture. It looks to me as if Hudson must have some special interest in her, to have two pictures of the same woman. We might find out who she is."
"That's important, surely; unless, of course, we can get hold of a better clue. But do you know what this is?" He held up the card.
"No, it looks to me like a fairy's lace handkerchief design or a sea-shell."
"That is a harmonic curve," said Astro. "Sometimes it's called a vibration curve, and it is traced by a compound or twin elliptic pendulum."
"What's that? I am getting farther away than ever."
"Suppose," continued Astro, "you tie one end of a string to a nail in the ceiling, while the other end is looped up to another nail, also in the ceiling. Now, from the lower point of this V, hang a string with a
