Geological Society. 37 1 



those phenomena which, he conceives, precede, attend, or follow 

 true volcanic earthquakes. 



Of the places where earthquakes have been felt without there 

 being anj^ traces of volcanic or trap rocks, but wheie gypsum is 

 known to occur, and in which, from that mineral being, in his opi- 

 nion, of comparatively easy renewal, he supposes, caverns exist, M. 

 Necker more particularly mentions Bale, Nice, Navarroux, Oleron, 

 Maulen, Bagnorre de Bigorre, and the Gave Maulen, in' the Vy. 

 renees ; he also alludes to the shocks which were felt at Clanssaye. 

 near St. Paul- trois- Chateaux, in the department of the Drome! 

 from the 1st of June, 1772, to the end of December, 1773, and he 

 states, that though Clanssaye stands upon a tertiary deposit, yet 

 It is probable that the gypseous formation of the hills to the east- 

 wards having a westerly dip may pass beneath it : likewise to the 

 earthquakes which affected Kronstadt in Transylvania, Odessa 

 Bucharest, Lembourg in Gallicia, and Kieff, with other towns in that 

 part of Russia, early in 1838, and in the vicinity of which -ypsum 

 IS believed to exist. Among the limestone tracts, in which caverns 

 abound, and eartliquakes are not unfrequently felt, M. Necker enu- 

 merates Fiume, Buchari, Trieste, Lissa in the Adriatic, and Fo- 

 ligno. 



In the above instances M. Necker supposes, that cavities havino- 

 been formed by the action of bodies of water, the roof gave wa/ 

 and, falling upon a solid floor, produced in the strata^a motion 

 which extended laterally and vertically, and gave rise to the pheno- 

 menon of an earthquake. He is further of opinion, that air con- 

 fined in the caverns being also set in motion by the subsidence of the 

 roof, would cause undulations in the overlying strata, lb illustrate 

 his views, M. Necker described the vibrations produced in the walls 

 of a house which he occasionally inhabits at Geneva, by the blows 

 of a blacksmith's hammer upon an anvil placed in a vault and 

 these vibrations always appeared to him completely analogous to 

 the motion which he experienced in the same room during the earth- 

 quake on the 19th of February, 1812. He likewise stated, that M 

 Virlet perceived, m a coal-mine, a shock resembling that of an 

 earthquake, by the falling in of some works at the distance of 

 a quarter of a league. 



With respect to the shocks felt at Nice, the author says that he 

 had carefully compared the list published by M. Risso, with the ac- 

 counts of eruptions of Vesuvius and Etna ; and that though some 

 of the earthquakes had preceded, by very short intervals, certain 

 powerful eruptions of those volcanoes; yet, in very many 

 instances, the shocks appear to have been quite independent • and 

 that a considerable number of eruptions, both of Vesuvius and 

 Etna, had not been felt at Nice. Hence, he infers, that, in this case 

 there may have been earthquakes due to volcanic, as well as non- 

 volcanic, agents ; and tliat Nice, standing upon a gyjisum forma- 

 tion, may have felt the effects of volcanic eruptions in consequence 

 of a predisposition in the undermined ground, without which thev 

 would not have been perceptible at the surface 

 2B2 



