534 THE POPULAR SCIENCE MONTHLY. 



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 be- 

 come 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. 



M. FOUQUfi'S SANTOKIN" AKD ITS EEUPTIOXS. 



MFOTTQUE, 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 exam- 

 ples 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 labora- 

 tory, 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 scorire. 

 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, particu- 

 larly in free hydrogen, arising in some cases from the separation of 



