American side the point selected was at about 40° north latitude and 70° longitude west of Greenwich—in other words, not far from the city of New York.
The work was begun in an immense chamber constructed under water; and to prevent the caving in of the walls of the tunnel as the digging progressed, a tube of considerable thickness and wonderful strength, made of the new metal, carbonite, was used. This metal, discovered—or, more properly speaking, invented—by the doctor, possessed all the qualities necessary for the purpose; for, while obtainable in large quantities, and easy to work, it had a strength compared with which the strength of the best steel was virtually nothing.
As it would have been out of the question to cast an eight-thousand-mile tube in a single piece, or, even if cast, to insert it afterward into the hole, some other plan had to be devised for accomplishing the desired result. But Dr. Giles had carefully studied out this part of the work, and by an admirable contrivance he had arranged to cast the tube little by little, immediately over the hole, and let it down as the boring progressed. In this way the top of the tube was always in a state of fusion, although the bottom was perfectly cold.
