214 PROCEEDINGS OF SOCIETIES. 



Per cent. 



Quartz, 20*51 



Orthoclase felspar, . . . . . 77*85 



98*36 



From the fact, that the felspathic trap of Benaunmore occurs in 

 columnar masses, it may be inferred to be probably of igneous origin : 

 it is massive, fine-grained, with rounded specks of quartz (globuliferous), 

 and small occasional facets of felspar ; brittle, of conchoidal fracture, 

 somewhat lamellar, and translucent on the edges, with a ringing clink, 

 and striking fire freely when struck with the hammer. 



I have lately had an opportunity, in conjunction with Dr. "Wilde of 

 Dublin, of examining a very large number of stone implements found 

 in various parts of Ireland, and I find that the different varieties of 

 siliceo-felspathic rocks were carefully sought out by the makers of these 

 implements. Among the most common varieties so used are the pure 

 pale-green felstone, and a mottled porphyritic variety of the same kind 

 of rock, streaked with pink felspar and dark-coloured metallic horn- 

 blende. 



In the collection of stone implements preserved in the Museum of 

 the Royal Irish Academy, there are also a number of stone implements 

 from Jamaica, formed of the same kind of felstone, which would appear 

 to have been particularly well suited to the purposes to which such im- 

 plements are supposed to have been applied. 



The felstones and siliceo-felspathic rocks of Ireland are only locally 

 abundant, and as the weapons made from this kind of rock are found in 

 all parts of Ireland, it is conjectured by antiquarians that an extensive 

 trade in, and manufacture of, these felstone celts and weapons must 

 have existed in former times in Ireland. This trade, if such existed, 

 must have been confined to Ireland itself, as there is scarcely a single 

 stone implement in the collection of the Irish Academy which cannot 

 be readily identified as made of an Irish rock ; and in many instances 

 the locality from which it was obtained can be assigned with tolerable 

 accuracy. 



WEDNESDAY, JUNE 10, 1857. 

 Edwaed "Weight, LL.D., M.R.I. A., in the Chair. 

 De. Geiffith read the following — 



LETTEE FEOM M. ADOLPHE BBONGNIABT TO ME. GEIFFITH, ON THE FOSSIL 

 PLANTS WHICH HAVE BEEN DISCOVEEED IN THE EOCKS AT THE BASE OF 

 THE CABBONIFEBOTJS SYSTEM IN IEELAND : COMMUNICATED TO THE SOCIETY 

 BY THE LATTEE. 



Paris, 5 Fevrier, 1857. 

 Monsietje, — J'ai recu dans le courant du mois de Decembre les 

 echantillons de plantes fossiles que vous avez bien voulu m'addresser, 



