184 Mr. Griffith on the Syenite Veins which traverse Mica Slate 



agreeing in this respect with the character which chalk usually presents, when found in contact with 

 common whin dikes. 



It is remarkable, that a small reniform mass of syenite, is included in the centre of this wedge of 

 chalk; but is much finer in grain than the usual mass of the syenite. It is evident from its external 

 appearance, that this small mass has not been rounded by attrition. 



In another specimen (No. 11.) the chalk is nearly enveloped by syenite ; and the minute pro- 

 jections at the point of contact are well developed. 



The specimen marked No. 12. exhibits a small portion of the syenite passing through the chalk 

 in the form of a vein ; and that numbered 13. contains five small portions of chalk insulated in the 

 syenite, and it is remarkable that the union at the contact is so perfect, that the chalk appears to 

 form an integral part of a compound rock. 



No. 5. 



Connexion of the chalk and syenite at Torr Eskert. a, mica slate ; d, chalk ; e, syenite. 



There are several other peculiarities which render this contact of syenite 

 and chalk very interesting, and which may probably give rise to much dis- 

 cussion. The most remarkable, is the occurrence of reniform or flattened 

 spheroids of the syenite included in the chalk. The positions of several of these 

 masses, are shown to the right of the sectional view No. 4, which was drawn 

 with great care, and accurately represents the facts when the last excavation 

 was made : any fresh excavation will of course cause a change in the detail, 

 but I have no doubt that the principal char acters will be continued. 



Included in the collection is a specimen (No. 14.) which exhibits two, detached, flattened masses 

 of syenite, resting on chalk. It might be argued from the smooth edges of this specimen, that the 



