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THE PQPULAR SCIENCE MONTHLY. 



of about six hundred fathoms depth ; as it rises to more than three 

 thousand feet above the surface, it represents a conical mass of cinders 

 and slaggy materials, six thousand feet high and more than four miles 

 in diameter at the base. The crater may be approached by a flat slope 

 called the Sciarra, which rises at an angle of 35 with the horizon, and 

 ends abruptly at its edge. The accompanying sketch (Fig. 2) was 



Fig. 2. The Crater of Stromboli as viewed prom the Side of the Sciarra during an 

 Eruption on the Morning op April 24, 1874. 



made from this point at the moment of an outburst. " Before the out- 

 burst, numerous light, curling wreaths of vapor were seen ascending 

 from fissures on the sides and bottom of the crater. Suddenly, and 

 without the slightest warning, a sound was heard like that produced 

 when a locomotive blows off its steam at a railway-station ; a great 

 volume of watery vapor was at the same time thrown violently into 

 the atmosphere, and with it there were hurled upward a number of 

 dark fragments, which rose to the height of four or five hundred feet 

 above the crater, describing curves in their course, and then falling 

 back upon the mountain. Most of these fragments tumbled into the 

 crater with a loud, rattling noise, but some of them fell outside the cra- 

 ter, and a few rolled down the steep slope of the Sciarra into the sea." 

 Spallanzani and other later investigators carried on their observa- 

 tions from a point whence they could look down into the bottom of 

 the crater, and, with a wind that would blow the vapors away, sit and 

 watch for hours the wonderful scene. From this point, the blacky 

 slaggy bottom of the crater is seen to be traversed by many fissures 

 or cracks, from most of which curling jets of vapor issue quietly and 

 gradually mingle with and disappear in the atmosphere. Besides, 

 there are several larger openings, varying in number and position at 

 different periods, from some of which " steam is emitted with loud, 

 snorting puffs, like those produced by a locomotive-engine, but far less 

 regular and rhythmical in their succession" ; from others, masses of 



