Page:Popular Science Monthly Volume 17.djvu/550

534 Goeschenen mouth, was diminished till it became, toward the end of the work, no greater than one atmosphere and an eighth at the front of the cutting. At Airolo it was necessary to enlarge the diameter of the perforators, and a much larger volume of air had to be spent to do the same work. The temperature at the front of the excavations rose to 91 during the last days of the operations, and greatly taxed the endurance of the workmen. Calculations have been made to the effect that, taking the work all through, each kilogramme of dynamite that was used corresponded with a cubic metre of rock that was removed. Among the gains to engineering which, it is claimed, have accrued from the enterprise, are the perfection of the machinery and tools for boring, and the training of a body of skilled workmen, who have become experts, able to determine, by merely inspecting a rock, how to deal most efficiently with it. The perforation of tunnels will in the future be a simpler, easier, and less costly operation than it has been heretofore. Since communication was established between the two galleries of the tunnel, a part of the mountain mass, 6,300 metres, or 20,475 feet from the southern entrance, has fallen in, killing and injuring several of the workmen.

 

FOUQUÉ, a professor in the College of France, has recently o published an elaborate work on the volcano of Santorin, which is considered one of the most remarkable and instructive examples of volcanic phenomena on the earth. He possesses excellent qualifications for this work, for he has made special researches on the volcano on three different occasions: first, when sent by the French Academy of Sciences in 1866; and twice afterward, in 1867 and 1875, under a commission from the Minister of Public Instruction. His account embraces the detailed recital of the observations which he made on the ground, and the description of his labors in the laboratory, analyses, and microscopic examinations, and contributes much to our knowledge on mooted questions respecting volcanic action.

The products thrown out in the recent eruption—which took place in 1866—like those of most other volcanic manifestations, may be divided into two categories: 1. Volatile matters exhaled in the form of gases and more or less easily condensible vapors; and, 2. Lavas overflowing in imperfect fusion, or thrown out as ashes and scoriæ. The gases varied greatly in composition during the course of the eruption. At the beginning, when they had not been subjected to the action of the air, they were rich in combustible elements, particularly in free hydrogen, arising in some cases from the separation of 