Queries and Answers* ^1 



greatly oblige me if your ingenious correspondent would state 

 the circumstances which have been called renewed symptoms 

 of action more fully, and also the authorities by which they 

 are supported. It could surprise no one who has attentively 

 examined the extinct volcanoes in central France to be in- 

 formed that they had broken forth into renewed activity after 

 a period of repose of many hundred, if not thousand, years. 

 Vesuvius is known to have had periods of repose for many 

 centuries ; and the lava of some of the volcanoes in Auvergne 

 appears as fresh as if it had been very recently erupted : in- 

 deed, it is very difficult to conceive how it could preserve such 

 a fresh appearance after exposure to the atmosphere for ages. 

 In my Travels in the Tarentaise, published in 1823, I stated 

 that " there is nothing in the appearance of the volcanoes of 

 Auvergne which can lead the observer to the conclusion that 

 their eruptions will never be renewed : the springs of hot water 

 in this district indicate that the source of subterranean heat 

 beneath it is not extinct. The most abundant and best known 

 of these springs are Mont d'Or and Vichy ; they have a tem- 

 perature of from 120° to 125°; and there are many other 

 springs of equal temperature. Should the volcanoes of Au- 

 vergne resume their activity, such an event would not be at 

 variance with our present knowledge of volcanic operations." 

 (vol. ii. p. 379.) Many of the eruptions in Auvergne must 

 have taken place in a recent geological epoch ; for lava has 

 flowed into the present valleys, and the heaps of fresh scoriae 

 that are spread loosely, near the mouths of the craters, and 

 volcanic vents to which they can be traced, prove that the 

 country has not been since subjected to diluvial currents, for 

 these would have swept them away. They prove, also, another 

 fact of some interest : many of the most recent eruptions appear 

 to have taken place from volcanic openings, which were closed 

 before craters could be formed round them ; for, had craters 

 been formed, and afterwards destroyed by inundations, the 

 same causes would have removed the lava and scoriae. In 

 other instances, volcanic craters v/ere formed by repeated 

 eruptions, and remain nearly perfect to the present time. 



The occurrence of volcanic mountains, over a space of 

 several thousand square miles in central France, should induce 

 us to receive with caution the accounts of the increase of 

 temperature in Artesian wells in PVance, at a rate of about 1° 

 of Fahrenheit for every 45 ft. of depth ; for this increase may 

 depend on local causes, which may not extend into other 

 countries. It is greatly to be regretted' that few experiments 

 on the temperature of Artesian wells have been made in Eng- 

 land. If any correspondent could furnish information on this 



Vol. VII. — No. 37. g 



