NOTES. CXXI 



each other. In the pieces collected by me in 1 802, and by Boussingault in 

 1831, the mass is partly light or greenish grey, shining like pitchstone, and 

 translucent at the edges; and partly black, almost like basalt, with great and 

 small pores with shining sides. The oligoclase sharply defined is embedded 

 in the mass ; appearing sometimes very distinctly in shining crystals forming 

 streaks in the planes of cleavage, and sometimes being very minute, and difficult 

 to recognise. The interspersed augites, which belong essentially to the rock, 

 are brownish and blackish green, and of very various sizes. Dark laminae of 

 mica, and black grains of magnetic iron of a metallic lustre, occur, but only 

 rarely, and probably accidentally. In the pores of a piece in which there is 

 much oligoclase there is some native sulphur, probably deposited from the all- 

 pervading sulphurous vapours. 



( 459 ) p. 322. " Le Volcan de Maypo (lat. austr. 34 15'), qui n'a jamais 

 rejete' de ponces, est encore e'loigne' de deux journe'es de la colline de Tollo, de 

 300 pieds de hauteur, et toute compose'e de ponces qui renferment du feldspath 

 vitreux, des cristaux bruns de mica, et de petits fragmens d'obsiclienne. C'est 

 done une eruption (inde'pendante), isole'e tout au pied des Andes et pres de la 

 plaine." (Le'op. de Buch, Description physique des lies Canaries, 1836, p. 470.) 



( 46 ) p. 322. Federico de Gerolt, Cartas geognosticas de los principales 

 Distritos minerales de Mexico, 1827, p. 5. 



( 461 ) p. 323. Compare On the Solidification and Formation of the Earth's 

 Crust, Kosmos, Bd. i. S. 178 180, and Anm. 7 on S. 425 (English edition, 

 p. 161163, and Note 137. The experiments of Bischof, Charles Deville, and 

 Delesse have thrown a new light on the folding and crevassing of the earth's 

 crust. Compare also the ingenious considerations of Babbage on the occasion of 

 his thermic explanation of the problem presented by the temple of Serapis, on 

 the north of Puzzuoli, in the Quarterly Journal of the Geological Society of 

 London, vol. iii. 1847, p. 186; Charles Deville, Sur la Diminution de Densite 

 dans les Roches en passant de 1'Etat cristallin a 1'Etat vitreux, in the Comptes 

 Eendus de 1'Acad. des Sciences, t. xx. 1845, p. 1453; Delesse, Sur les Effets de 

 la Fusion, t. xxv. 1847, p. 545; Louis Frapolli, Sur le Caractere ge'ologique, in 

 the Bulletin de la Soc. Geol. de France, 2 e se'rie, t. iv. 1847, p. 627; and above 

 all, Elie de Beaumont, in his important work, Notice sur les Systemes de 

 Montagnes, 1852, t. iii. The following three sections deserve especial attention 

 from geologists : " Considerations sur les soulevements dus a une diminution 

 lente et progressive dn volume de la Terre, p. 1330; Sur Vecrasement trans- 

 versal, nomme refoulement par Saussure, com me une des causes de 1'e'levation 

 des chaines de montagnes, p. 1317, 1333, and 1346; Sur la contraction que 

 les roches fondues eprouvent en cristallisant, tendant des le commencement du 



