110 



J. W. Judd — On Yolcanos. 



•which have been situated on a line directed N.W. and S.E. ; and that 

 the eruptions to which each new cone has owed its origin have, at 

 the same time, destroyed the northern portion of the pre-existing 

 one. The oldest crater-ring is composed of ordinary trachytic lavas, 

 exhibiting all the character- 

 istics and variations found 

 among the products of the 

 second period of eruption 

 in the Lipari Islands; but 

 the newer ones are found to 

 present materials becoming 

 continually more basic in 

 composition, till at last they 

 approximate to basalts and 

 dolerites resembling those 

 of Stromboli. The struc- 

 ture of this part of the 

 island will be made clearer 

 by a reference to the accom- 

 panying plan of the island, 

 Fig. 10. 



Encircled by the four 

 older crater-rings just de- 

 scribed, and separated from 

 them by a semicircular 

 valley ("Atrio ") deeply 

 covered by volcanic sand, 

 rises the active cone of Vul- 

 cano. This is not, as a 

 glance at the sketch will 

 show, a simple cone with a 

 summit crater like that of 

 Vesuvius, but a truncated 

 conical mountain, in which 

 the present crater occupies 

 an excentric position. No 

 one examining the upper part of the mountain can fail to perceive 

 there the vestiges of a number of craters which have been successively 

 formed and destroyed ; and that the position of the central axis of 

 eruption must have been subject to constant variation. These con- 

 clusions are confirmed, as we have seen, by those accounts of the 

 state of the mountain in earlier times which have come down to us. 



The highest point of the active volcano is situated on the north- 

 east of the crater, and is 1266 feet above the sea-level. The lowest 

 point of the crater rim, that over which the road is carried by which 

 access is gained to the interior, is 882 feet high, while the floor of 

 the crater is 532 feet above the sea-level. 1 



1 There exists a remarkable discrepancy between some of the estimates of the 

 height of the floor of the crater of Vulcano above the sea-level. Deville states it to be 

 837 feet, while Mr. Mallet gives it as only " a few feet," stating the depth of the 

 crater to be from " 1100 to 1200 feet." My own measurements with the aneroid were 

 repeated on three different occasions, and varied only between 497 and 535 feet. The 



Fig. io. — Plan of the Island of Vulcano, based on the 

 map published by the Italian Government.— a. The 

 four outer crater rings, culminating in Monte Sara- 

 ceno. b. The Atrio surrounding the modern cone. 

 c. The great crater, d. The smaller crater of the 

 Fossa Anticcha. e. The obsidian lava-stream (of 

 I 77S)- /• The Faraglione dellaFabbrica. g. Lava- 

 fields of Vulcanello. h. The cone of Vulcanello with 

 its three craters. 



