CXX11 NOTES. 



refroidissement du globe a rendre sa masse interne plus petite que la capacite" 

 de son enveloppe exterieure, p. 1235. 



( tt2 ) p. 324. " Les eaux cbaudes de Saragyn, a la hauteur de 5260 pieds, 

 sont remarquables par le role que joue le gaz acide carbonique qui les traverse a 

 1'e'poque des tremblements de terre. Le gaz a cette e*poque, comme 1'hydrogene 

 carbone de la presqu'ile d'Apcherori, augmente de volume, et s'echauffe avant et 

 pendant les tremblements de terre dans la plaine d'Arddbil. Dans la presqu'ile 

 d'Apche'ron la temperature s'eleve de 20 jusqu'a 1'inflammation spontane'e au 

 moment et a 1'endroit d'une Eruption igne'e, pronostique'e toujours par des trem- 

 blements de terre dans les provinces de Che'makhi et d'Apche'ron." (Abich, in 

 the Melanges physiques et chimique's, t. ii. 1855, p. 364 and 365.) (Compare 

 Kosmos, Bd. iv. S. 223; English edition, p. 175.) 



(*") p. 324. W. Hopkins, Researches on Physical Geology, in the Phil. 

 Trans, for 1839, Ft. II. p. 311 ; for 1840, Pt. I. p. 193; and for 1842, Pt. I. 

 p. 43 ; and also On the requisite Conditions of Stability of the exterior Surface 

 of the Earth, in the Theory of Volcanoes in the Report of the Seventeenth Meet- 

 ing of the British Association, 1847, p. 4549. 



C 64 ) p. 324. Kosmos, Bd. iv. S. 3538, Anm. 3336 (English edi- 

 tion, Notes 3336); Naumann, Geognosie, Bd. i. S. 66 76; Bischof, 

 Warmelehre, S. 382; Lyell, Principles of Geology, 1853, p. 536 to 547, and 

 562. In the very instructive and pleasant work, Souvenirs d'un Naturaliste, 

 par A. de Quatrefages, 1854, t. ii. p. 464, the upper* limit of the fluid molten 

 strata is brought up to the small depth of 20 kilometres : " puisque la plupart 

 des silicates fondent deja a 666 cent." Gustav Rose remarks that " this low 

 estimate is based on an error. The temperature of 1300 cent., which Mitscher- 

 lich gives as the melting point of granite (Kosmos, Bd. i. S. 48; English edition, 

 p. 27, and Note 13), is certainly the least that can be taken. I have several 

 times had granite put into the hottest parts of the porcelain furnace, and it has 

 always been but imperfectly fused. Only the mica is fused, with the felspar 

 forming a glass with many bubbles ; the quartz becomes opaque, but does not 

 fuse. It is the same with all kinds of rock which contain quartz, and, indeed, 

 this may be used as a test for discovering quartz in rocks in which it exists in 

 quantities so small as not to be discernible by the naked eye, ex. gr. in the 

 Plauen syenite and in the diorite which we brought back with us, in 1829, from 

 Alapajewsk in the Ural. All rocks which do not contain any quartz, or any 

 minerals containing as much silica as does granite (for example basalt), when 

 exposed to the same heat as porcelain, fuse more easily than granite into a per- 

 fect glass ; but they do not do this over a spirit lamp with a double current of 

 air, which yet is certainly capable of affording a temperature of 666 cent." In 



