ON THE OLDER ROCKS OF ANGLESEY. 231 



7. Any one of these rocks, whether granite, syenite, or diorite, or 

 whatever they may be called, puts on a foliated character in places, usually 

 towards the margin of the mass. 



8. There are rocks in this old series of an essentially basaltic 

 structure, i.e., consisting of acicular crystals of felspar in a less differen- 

 tiated ground mass. 



9. The fragments which occur in the breccias of the series between 

 Bangor and Carnarvon can mostly, if not entirely, be identified with 

 rocks from Anglesey, including the above basaltic rock, except those 

 which are derived from the felsites of the same series. 



10. The limestones of the group are remarkably pure, having either 

 a schistose or mosaic structure ; they have, however, in some cases the 

 interstices filled with bfematitic dust, which, when quartz is present, forms 

 jasper. The only exception to this purity is an oolitic limestone at Llan- 

 badrig, in which oolitic grains, often grain within grain, are imbedded in 

 the more crystalline calcite. 



11. In connection with the felsites occurring on the mainland must 

 be recognised a rock occurring, amongst other places, near Beaumaris, 

 which may be called a felsite grit. It is truly clastic, and may be a 

 cleaved rock containing foreign fragments ; but the matrix is so entirely 

 formed of felsitic material that it has the aspect of a true felsite. 



12. The peculiar polarising tints which are characteristic of pressure 

 are met with in many of the rocks, but their development is so sporadic, 

 even in the same rock, that their significance cannot yet be completely 

 determined : it is less common in the granitic and allied rocks than in 

 the schist. 



In order to carry on the investigation of these rocks to a conclusion 

 the Committee de.sire to be reappointed. 



Second Report of the Committee, consisting of ProfeBsors Tilden 

 and Armstrong {Secretary), appointed for the purpose of in- 

 vestigating Isomeric Naphthalene Derivatives. (Draivn up by 

 Professor Armstrong.) 



Valuable contributions to our knowledge of the naphthalene derivatives 

 have been made during the past year by Bamberger, Cleve, Ekstrand, 

 Porsling, Guareschi and Biginelli, and others ; my own investigations 

 have also progressed very satisfactorily : and fi^om the results obtained it 

 is more than ever obvious that the information to be derived from the 

 study of naphthalene derivatives will be of considerable importance, as 

 it will unquestionably serve to throw light on the nature of the changes 

 involved in the formation of substitution derivatives generally and on 

 laws of substitution. 



Sulplionation of a-mono-derivatives. — The behaviour of a-chloro- and 

 bromonaphthalene was referred to in the last report ; that of u-iodo- 

 naphthalene has since been found to be precisely similar, as this com- 

 pound yields the 1:4 sulphonic acid as main product together with an 

 isomer. The latter, however, has not yet been obtained in sufficient 

 quantity to satisfactorily determine its specific characters. The 1:4 

 sulpho-chloride crystallises in massive prisms, melting at 123° ; bromine 



