358 GRANITES OF DIFFERENT AGES. [Ch. XXV. 



numerous observers, amongst the earliest of whom we may cite 

 Von Buch, who discovered in Norway a mass of granite over- 

 lying an ancient secondary limestone, containing orthocerata 

 and other shells and zoophytes*. 



A considerable mass of granite in Sky is described by 

 Dr. Macculloch as incumbent on limestone and shale, which 

 are of the age of the English lias f . The limestone, which, 

 at a greater distance from the granite, contains shells, exhi- 

 bits no traces of them near the junction of the igneous rock, 

 where it has been converted into a pure crystalline marble J. 



This granite of Sky was at first termed ' Syenite/ by which 

 name many geologists have denominated the more modern 

 granites ; but authors have entirely failed in their attempt to 

 establish a distinction between granites and syenites on minera- 

 logical characters. The latter have sometimes been defined to 

 consist of a triple compound of felspar, quartz, and hornblende, 

 but the oldest granites are very commonly composed of these 

 ingredients only. In his later publications Dr. Macculloch has 

 with great propriety, we think, called the plutonic rock of Sky 

 a granite . 



In different parts of the Alps a comparatively modern granite 

 is seen penetrating through secondary strata, which contain 

 belemnites, and other fossils, and are supposed to be referrible 

 to the age of the English lias. According to the observations of 

 M. Elie de Beaumont and Hugi, masses of this granite are some- 

 times found partially overlying the secondary beds, and altering 

 them in a manner which we shall describe more particularly 

 when we treat of the changes in composition and structure su- 

 perinduced upon sedimentary deposits in contact with Plutonic 

 rocks|| (see wood-cut, No. 90, p. 371). 



In such examples we can merely affirm, that the granite is 



* Travels through Norway and Lapland, p. 45. London, 1813. 

 f See Murchison, Geol. Trans., 2nd Series, vol. ii. part ii. p. 311321. 

 j Western Islands, vol. i. p. 330. 

 $ Syst. of Geol., vol. i. p. 150. 



|| Elie de Beaumont, Sur les Montagnes de 1'Oisans, Mem. de la Soc. d'Hist. 

 Nat, de Paris, tome v. Hugi, Natur, Historische Alpenreise, Soleure, 1830. 



