100 West One Hundredth Street, and the floorwalker says, 'Sorry, Mr.
Smith, but we don't know you,' what then?"

"Just flash a few letters on him," said the girl. "Letters and
envelopes."

"Where do you get 'em?" asked Peabody.

"Just write them, silly, and send them to yourself through the mail."

"That's all right," retorted the "second story man." "But how can I mail
myself a letter to 100 West One Hundredth Street _when I don't live
there_?"

Mrs. Parker smiled in a superior manner.

"I'm glad I can put you wise to a new game, I invented it myself. You
want letters of identification? In different names and addresses on
different days? Very good. Buy a bundle of stamped envelopes and write
your own name and address on them _in pencil_. When they arrive rub off
the pencil address. Then if you want to be John Smith of 100 West One
Hundredth Street, or anybody else, just address the cancelled envelope
_in ink_."

"Mabel," said Peabody with admiration, "you've got the 'gray matter' all
right. You can have _me_, if you can deliver the rest of the goods."

[Illustration: FIG.3.--A letter-head frill of Mabel Parker's.]

"There's still another little frill," she continued, pleased at his