SERPENTINE PORPHYRIES. 173 



in basa'lt. It is the same with beds, in appearance regular, 

 seen between sedimentary layers ; observation shows they are 

 only ramifications of veins. This is clearly seen at Trotternish, 

 in the isle of Sky (Jig- 283), where a great seam of trap commu- 

 nicates with a bed of similar matter, which is itself divided further 

 on into three branches. Hence it is evident the intercalation of 



Fig. 283. Injection of trap into sedimentary rocks. Isle of Sky. 



tra'ppean rocks in arena'ceous beds is the result of an injection, 

 which followed the separation of the beds of the sedimentary de- 

 posit to a greater or less distance, as in the case of the basa'lls of 

 Villeneuve-de-Berg (fig. 278). 



18. Ser'pentine and Diallage ; different porphyries. Magne- 

 sian rocks, called ser'pentine, often accompany trap and di'orite ; 

 they very frequently form seams or veins of themselves. Ser'- 

 pentines and eu'photides are often injected in all manners into cal- 

 careous deposits belonging to the jnra'ssic period. Sometimes 

 they form veins, sometimes thick strata ; they often present brec- 

 cias of every species which constitute the marbles called verd 

 anti'que, verd d' 1 Egypt e, &c. The limestones mingled with these, 

 rocks are all in the saccharoid state, and furnish the most beautiful 

 statuary marble and the most brilliant breccias ; yet, if we ex- 

 amine them carefully, we find they belong entirely to the compact, 

 and more or less earthy limestones, the surrounding deposits of 

 which they are evidently a continuation. The schistose clays and 

 sandstone, which alternate with the last, are found converted in 

 the others into jaspers of different varieties. 



The appearance of pyroxenic rocks, mela'phyrieg (porphyries, the con- 

 stituents of which are united by a black cement), and other porphyries 

 which belong to them, is productive of circumstances of the same kind ; 

 M. de Buch long- since pointed them out in the Tyrol, and subsequently in 

 upper Lombardy. They arc also found all along 1 the Alp?, and are repre- 

 sented in the same direction in Provence in the midst of the mountains of 

 Esterel: all is upturned in the neighbourhood of these rocks, which, in 

 "coming to day," have upheaved around them calcareous deposits of dif- 

 ferent formations, dislocating and placing them in the most abnormal posi- 

 tions. Wherever they arc in contact with these porphyries, and to a con- 

 siderable distance beyond, limestones are transformed into dolomite, and in 

 such a manner that the same deposits are of simple limestone in some parts, 

 and of dolomite injected into those which are near to rocks of crystalli/a- 

 tion. What is most remarkable is, that the few organic remains met. in 



1 7. How does trap resemble basa'lt J 

 IS. What is serpentine? Wh^t is verd antique ? 

 15* 



