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phyries containing vitreous feldspath and horn- 

 blende *, the pbonolite rjr 3 the greenstone, the 

 amygdaloids, and the basalt have forms almost 

 as invariable as simple crystallized substances. 

 In the Canary islands, and in the mountains of 

 Auvergne, in the Mittelgebirge in Bohemia, in 

 Mexico, and on the banks of the Ganges, the 

 formation of trapp is indicated by a symmetrical 

 disposition of the mountains, by truncated cones, 

 sometimes insulated, sometimes grouped ^, and 

 by elevated plains, both extremities of which are 

 crowned by a conical rising. 



The whole western part of Lanzerota, of which 

 we had a near view, bears the appearance of a 

 country recently overturned by volcanic erup- 

 tions. Every thing is black, parched, and strip- 

 ped of vegetable mould. We distinguished, with 

 our glasses, stratified basalt in thin and steeply 

 sloping strata. Several hills resembled Monte 

 Novo, near Naples, or those hillocks of scoria 

 and ashes, which the opening earth threw up in 

 a single night at the foot of the volcano of Jo- 

 rullo, in Mexico. In fact, the Abbe Viera § 

 relates, that in 1730 more than half the island 

 changed it's appearance. The great volcano, 

 which we have just mentioned, and which the 



* Amphibole of Haiiy. 

 t Porphyrschiefer of Werner. 

 X Montigemelli, Zwillinsberge. 

 § Viera, t. ii. p 404, 



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