122 SYENITE. 



loftiest pinnacles on our globe, and constitutes, at the same 

 time, the skeleton or framework on which most of the other 

 deposits repose. It likewise occurs in the state of beds of 

 irregular shape, among strata of gneiss and other ancient 

 stratified deposits. It is also met with in veins, intruding 

 into rocks of all ages, from those granitic injections which are 

 found to penetrate masses of granite older than themselves, up 

 to similar intrusions into the secondary and tertiary strata. 

 It has been discovered in the Pyrenees, penetrating a rock of 

 the same date as the chalk; syenite, which maybe considered 

 a variety of granite, has been found overlying the chalk at 

 Weinbohla, in Saxony, as well as in the county of Antrim, 

 in Ireland ; while Mr. Darwin has observed, that the granite 

 of the Cordilleras of South America has been fluid as re- 

 cently as the tertiary period, and has altered and contorted 

 strata of that date. Granite veins are often found inter- 

 sected by veins of granite, still newer than themselves, and 

 the rock occasionally occurs as dikes, which are, in fact, 

 similar ramifications on a larger scale, the essential difference 

 being that the dikes continue for a longer distance, while 

 the veins thin out into filaments. Indeed, every mass of 

 granite which forms the central peak of a mountain-chain, is 

 no other than a dike on an enormous scale, which has burst 

 through the superincumbent strata, and borne them upwards 

 in its elevation. While granite is supposed to have generally 

 been erupted in a fluid condition, instances occur in which it 

 has evidently been protruded in a solid state. The proofs of 

 this circumstance are afforded by the absence of any dikes, 

 veins, or filaments ramifying into the surrounding rocks, as 

 well as by the presence of conglomerates and breccias result- 

 ing from the grinding and attrition of such rocks by the 

 elevation of the granitic mass. The localities of granite, in 

 England, are Cumberland, Cornwall, and Devon ; in Scot- 

 land, the Highlands and the Isle of Arran ; and in Ireland, 

 the Mourne mountains. 



SYENITE. This is granite in which mica is replaced by 

 hornblende, which gives a darker hue to the mass. Its name 

 is derived from the city of Syene, in Upper Egypt, where it 

 largely abounds. The Malvern Hills, in Worcestershire, 

 belong to this group. 



GREENSTONE. This term is applied to those rocks which 



