INTRODUCTION. 



Space of 



volcanic 



appearances. 



' c Mr. Watt having fused a large quantity of basalt, in the 

 centre of the mass which was slowly cooled, the crystals of 

 basalt were large ; but they grew less as they approached the 

 surface, which was amorphous and vitrified. 



" The lava emitted from volcanoes is speedily decomposed 

 by the action of moisture and the atmosphere, and forms the 

 most fertile soils. No countries are more productive than 

 those in the vicinity of volcanoes, if below the line of per- 

 petual snow. The volcanic island of Santorin, which was 

 raised in the Archipelago in one night, in the year 1770, is 

 now in part covered with a luxuriant vegetation, and no 

 country in Europe is more productive than the lower decli- 

 vities of Etna. 



<( The operations of nature are on a scale too extended to 

 be measured by days or years : they require ages to produce 

 their full effect. What appears destructive and desolating at 

 the first view, is found on a more comprehensive examination 

 to be attended with permanent advantage. The lava and the 

 ashes which burned Herculaneum and Pompeia, have fur- 

 nished abundant harvests for fifteen centuries. The evils 

 that nature inflicts are transient, but her benefits are of last- 

 ing duration." 



It is unnecessary to warn the reader that this extract is not 

 from the hand of the excellent author, and that of course it 

 is only the general current of the ideas which deserves atten- 

 tion. But as the Germans have too much restricted, or 

 rather annihilated, the influence of volcanoes, it seems here 

 to be rather too much enlarged : for if we suppose two hun- 

 dred existing volcanoes, and compute the medium of their 

 agency at thirty miles each, the amount will be six thousand 

 square miles, or at the most equal to the island of Sicily, 

 about seven thousand two hundred. But the extinct vol- 

 canoes would probably more than double this extent ; and it 

 seems certain that in the chaotic and ancient state of the 

 globe, before the component substances had acquired their 

 present solidity and temperature, numerous volcanoes must 

 have existed, which have been totally and radically extin- 



