Proceedings of the British Association. 243 



shausen. — The author illustrated his remarks by maps and diagrams 

 of Mount Etna, exhibiting by different shades of colour the dates of 

 streams of lava which had flowed from 215 different eruptions, and 

 the exact position of all the minor craters, 750 in number, dotted over 

 the region surrounding the principal elevation. The maps were, on a 

 scale of — — of nature, and were still in manuscript, although now 

 in the process of being engraved in Germany, accompanied by a de- 

 tailed description of all the geological and topographical phenomena 

 connected with it, illustrated by very numerous and elaborate draw- 

 ings. This work is the result of above nine years' labour, chiefly on 

 the spot. At one time Baron "Waltershausen remained forty-two 

 days in the neighbourhood of the summit, making his survey and 

 observing the changes of the principal crater. The map contains a 

 representation of the dykes of the Val del Bove. Those which are of 

 diorite manifestly diverge from a central point a long way to the east- 

 ward of the present cone, which point the author supposes to indicate 

 the centres of the elevatory forces at the time of the dioritic forma- 

 tions. The oldest rock in Etna appears to be a whitish trachyte, 

 which appears in the Val del Bove, and at one or two other points on 

 the eastern side. 



Sir H. De la Beche stated that these maps had been laid down 

 from trigonometrical survey, and were the most beautiful specimens 

 of such work he had seen. He also alluded to the evidence of a cra- 

 ter of elevation entirely different from the small crater of eruption, 

 and that the shifting of this principal crater was shown by the radia- 

 tion of dykes from more than one point ; these dykes being simply 

 cracks filled with molten rock, forced up from beneath.— Baron von 

 Buch remarked, that two circumstances were particularly worthy of 

 notice — first, that the greater part of the lava did not flow from the 

 principal crater, but from points as much as five miles distant ; and 

 secondly, that all the cracks formed during eruptions went upwards 

 to the central crater, — Prof. J. Forbes observed that the section seen 

 in the Val del Bove, exhibited most completely the mode of formation 

 of the volcano, and afforded the best criterion for judging of the 

 accuracy of the theory of volcanic elevation propounded by Von 

 Buch. He pointed out the evidence of the progressive motion of the 

 centre of elevation from ancient periods to the present time, a change 



