I stared down at the table. In what other way might I read a meaning into the numbers? I picked up an envelope and began to toy with it unconsciously. It was addressed to St. Hilary. It was literally covered with erasures and directions, and had followed him half around the world. But it had found him at last, though some of the directions were of the vaguest. We ought to be as clever as a postmaster. Aside from the extraneous aids of the directory, what methods would a postmaster use?
Mechanically I began to trace the ordinary and palpable clues to the destination of any letter. First of all, there is the state or country. That is as vague as the earth itself. But the state is narrowed down to the city in the state, and the city to the street––
“I believe I have found a solution that will hold water at last, St. Hilary!” I cried.
He blinked at me skeptically.
“Let us hear it by all means.”
“Take the address on the envelope. It has suggested a possible solution to the numbers. First of all, there is the country. The country is narrowed down to the city of the country. Next comes the number of the street in the city. After that the house in the street. In other words, the direction of an envelope is narrowed to more and more defined limits.”
“An extremely accurate but not a startlingly original presentation of facts, dear boy. The connection between this envelope, for instance, and the da Sestos casket?”
“Call Venice the state; the city, the Grand Canal. Your street will then be the seventh canal; the number of the street will be the house of the landmark.”
St. Hilary’s dark eyes snapped. He was thoroughly interested at last. He drew toward him the map of Venice again. He pushed it away with an exclamation of disgust.
“Ingenious again, but not conclusive. The seventh canal flowing into the Grand Canal is a cul-de-sac. Its length is not a hundred yards, and it leads merely to the Campo San Stefano.”