INTRODUCTION. 45 



The submarine eruptions at Santorin, in 1707, were fully 

 reported by Vallisnieri and Lazzaro Moro, but Mount Vesuvius 

 was the volcano which proved the chief source of interest 

 throughout the sixteenth, seventeenth, and eighteenth centuries, 

 when it was visited by cultured men of all countries during 

 their travels in Italy. 



The Royal Librarian in Naples, Father della Torre, in 

 1755 compiled a complete record of all the active eruptions 

 and other phenomena observed at Vesuvius from 79 A.D.to the 

 middle of the eighteenth century. Valuable information about 

 Vesuvius, Etna, and the surroundings of Naples is contained 

 in the letters addressed by the English ambassador at Naples, 

 Sir William Hamilton, to the President of the Royal Society in 

 London. And the handsome volume, with fifty-nine coloured 

 plates, by the same author still holds its reputation as one 

 of the most trustworthy historical and scientific accounts of 

 Mount Vesuvius. 



The progress of travel in the sixteenth, seventeenth, and 

 eighteenth centuries gradually added a knowledge of the wide 

 distribution of volcanic mountains. Besides the S. European 

 volcanoes and Mt. Hecla in Iceland, geographers recognised 

 the active volcanoes of Kamtschatka, of Japan, the Sunda 

 Isles, the Philippines, the Canary Isles, the Azores, the West 

 Indies, Mexico, and Peru. 



Meantime Guettard's discovery of the extinct volcanoes of 

 Auvergne gave a new impulse to the mineralogical study of 

 the volcanic rocks in that vicinity. 



Nicolas Desmarest, a French Professor, opposed Guettard's 

 erroneous conception that the Auvergne basalt pillars had 

 crystallised from a watery fluid, and demonstrated the 

 resemblance of the Auvergne basalt to certain recent lavas. 

 He showed that in the Auvergne district true basalt is 

 frequently covered by volcanic ashes or rests upon ashy 

 material, that the transition in the field from basalt to 

 true lava is quite gradual, and that the basalt everywhere 

 presents the character of a volcanic mass that has been 

 originally molten and has afterwards consolidated. He 

 thought, further, that basaltic rock frequently showed transitions 

 to porphyry (trachyte and phonolite), and this again into 

 granite, and concluded that all these rocks probably originated 

 from a molten state, the granite representing rock solidified ! 

 from a less fluid state of the volcanic magma, and basalt 1 



