ON ITS EXTERIOR. VOLCANOES. 405 



the influence on the constitution of the atmosphere, 

 and on its climatic, and especially its electric, delations 

 would assuredly be very sensible; but the non-simul- 

 taneity of the eruptions diminishes the effect and 

 restricts it within very narrow, and for the most part 

 merely local limits. In great eruptions there arise 

 around the crater, in consequence of evaporation, vol- 

 canic storms, which, accompanied by lightning and 

 violent falls of rain, often occasion devastation ; but 

 an atmospheric phenomenon of this kind has no gene- 

 ral results. For, on account of the magnitude of .the 

 phsenomenon, I have always regarded as exceedingly 

 improbable the opinion which is even still sometimes 

 expressed, attributing the remarkable darkness which 

 for many months, from May to August in 1783, over- 

 spread a -considerable portion of Europe and Asia as 

 well as of the north of Africa (while on the high moun- 

 tains of Switzerland the sky was seen clear and unob- 

 scured), to great volcanic activity in Iceland, and to the 

 earthquake in Calabria. Where earthquakes embrace a 

 wide area, a certain influence on the period of the com- 

 mencement of the rainy season, as in the highlands of 

 Quito and Eiobamba in February 1797, and the south- 

 east of Europe and Asia Minor in the autumn of 1856, 

 may be more readily admitted, than extensive meteoro- 

 logical effects from an isolated volcanic eruption. 



In the subjoined table the last column but one in- 

 dicates the number of volcanoes which have been cited 

 in the preceding pages; and the last column (within 

 brackets) indicates the portion of them which have 

 given proofs of activity within recent times. 



