Dr. Giles had managed to maintain his calm outward appearance; but now, as the tunnel approached completion, he could no longer conceal his agitation, but paced to and fro like a caged animal.
"Why, whatever is the matter with you, doctor?" asked James Curtis, who had dropped in, as usual, with his daughter Flora, who was now a charming girl of fifteen, and as brimful of sympathy as ever.
"The matter is, James, that to-day I am to learn whether or not the tube is finished, or whether it will require five more years of hard work to complete it."
"Why, what in the world do you mean? Are n't your two tubes now within a mile of each other, and won't they touch to-night?"
"I sincerely hope so," said the doctor; "but it is quite possible that they will never meet."
"How so?" inquired Mr. Curtis, quickly.
"Well, the thing is this. Even in constructing a tunnel a few miles long, our engineers, if they begin work at both ends at once, find the greatest difficulty in making the two holes meet. Moreover, in their tunnels a small error is of no material consequence. Now in my case I am digging
