322 D. Forbes — On Vokanos. 



When, owing to the disruptions of the ground around volcanos, 

 the water from springs, rivers, lakes, or the sea itself, is brought 

 into contact with the heated mineral matter below, we have the pro- 

 duction of the so-called mud volcanos,-or of fissures seeding forth 

 torrents of heated mud and water, and often throwing out numbers 

 of fishes which had lived previously in these sources. The Gey- 

 sers of Iceland present somewhat similar phenomena, but on this 

 occasion, time-will not permit these subjects being treated in detail. 



Whilst some volcanos, like Stromboli (the lighthouse of the 

 Mediterranean, as it was called by the ancients), have continued in 

 incessant activity from the oldest historical periods down to the 

 present day, the eruptions of others are only known to have taken 

 place at long intervals. Vesuvius, although imagined by Strabo to 

 have had a volcanic origin, was not known even by tradition to have 

 ever been in eruption until the year 79, when Pompeii was over- 

 whelmed by It. Since that time, however, up to the present date, it 

 has given ample proofs of its volcanic activity ; yet its history shows 

 several intervals of a century, and one of more than two centuries, 

 ■in which no eruption took place. No outbreak of the volcano 

 Sangay, in Ecuador, is recorded before 1728, since which year it has 

 been in continued activity ; and Krabla, in Iceland, also remained at 

 rest for several hundred years before 1724. In fact, it may be 

 safely affirmed that it is quite impossible for us to know whether any 

 volcano at all is entitled to be regarded as really extinct. 



Even for ages after the last outburst of lava it is found that 

 smoke and acid vapours continue to be given off from most volcanic 

 vents, and the extraction of the sulphur found in the <;raters, and 

 sublimed into the fissures around dormant volcanos, forms in many 

 countries an important branch of industry. 



Although as yet I have confined my remarks altogether to terres- 

 trial volcanos, it must not be supposed that the depths of the sea are 

 exempt from such visitations, and in the last few years we have had 

 several prominent examples to the contrary in different parts of the 

 world. Submarine volcanos were well known to the ancients. Pliny 

 and older writers refer to those in the Mediteri'anean which threw 

 up the islands of Delos, Ehodes, Anappe, Nea, etc. In the Cyclades, 

 very curious examples have occurred, both in very ancient and in 

 the most recent times. Of these islands, Therasia is recorded to 

 have been formed in the third century b.o. ; as also, somewhat later 

 in the same century, the island of Thera, now called Santorin ; sub- 

 sequently Hiera, 91 b.c, and then Thea, a.d. 19, appeared, which 

 last two were in 726 united by an eruption, and together form the 

 present island of Kaimeni. In 1575, a smaller island, called Little 

 Kaimeni, showed itself, around which in 1650 numerous other islets 

 were thrown up, which were united to Little Kaimeni during the 

 eruptions which continued from 1707 to 1812, when the island, thus 

 increased in size, became known as New Kaimeni. Finally, the last 

 eruption (still going on) which commenced 28th January, 1866, 



S resented us on the 2nd February with a new island, now called King 

 eorge's Island, from the present King of Greece, which, according 



