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called, of 279 feet, was sufficient at the northern end, while at the southern a fall of 531 feet was employed.

The air-compressor used at the St. Gothard had been improved to such an extent by Professor Colladon, of Geneva, that it is often called the Colladon compressor. One of the devices employed was this: The compression of air rapidly generates heat, and to reduce the temperature of the compressing cylinder a circulation of water was kept up all around it. The piston and piston-rod were hollow, and water was introduced into them in like manner. In the shape, finally, of fine spray, water was injected into the cylinder, and thus brought into contact with the air itself.

Not a little interest attaches to circumstances connected with the invention of Sommeiller. This engineer bad two associates, Grandis and Grattoni. All were Italians, and all worked together in the evolution of the problem. No statement has appeared designating the part, or significance of the part, taken by each—a fact somewhat to their credit. Of the three, Sommeiller, however, came to be the best known; a member of the Sardinian Parliament, he appeared in public, as his associates did not. His name suggests a French, or, at least, Savoyard origin, but the inventor was a Piedmontese, and in his writings used the Italian tongue.

The St. Gothard Tunnel is by some considered the most remarkable engineering work extant,^[1] Mr. W. W. Evans, already quoted, writing in 1879—and whatever he says upon this point refers to his fixed idea that the proper route for an interoceanic canal was San Blas—says:

Our weak-kneed people, who get frightened at the idea of a tunnel, should go to Europe, and study tunneling as done there. J found over two hundred tunnels between Nice and Spezzia on the edge of the Mediterranean, cut and used for a very limited railway travel. The line of the St. Gothard Railway is a perfect marvel for tunnels. Nearly one fourth of the whole line is in tunnels. The great or summit tunnel is nine and a half miles long; and in seven places on the line—three on the Swiss side of the St. Gothard, and four on the Italian side—they have tunneled into the sides of the mountain in great entire circles of a thousand metres diameter, merely to get distance and keep the line to their fixed maximum gradient of one in forty, or say one hundred and thirty-two feet to the mile. And what is all this terrible expenditure for? Why, merely to rehabilitate the trade which the Suez Canal has opened, and which the people of the Mediterranean enjoyed, and out of which they built their great cities.

Whether or not we consider the connection as immediate between Suez and St. Gothard, as our author does, it is to be admitted that the introduction of new processes in the case of these tunnels and consequent acceleration of the work naturally encouraged those, like Mr. Evans and Major Shelbourne, intent upon the cutting of a tunnel for ships. Nor would the larger dimensions of such a work necessarily

1. Appletons' "Annual Cyclopædia," 1881, p. 819.