i 



Royal Irish Academy. 107 



dark green, but frequently veined and mixed with many other mi- 

 nerals. 



In the centre of the exposed portion of the dyke rises a large vein 

 of nearly white hornstone, presenting very interesting characters. It 

 contains no imbedded minerals, and is homogeneous in structure, but 

 with a lamellar or pseudo-crystalline arrangement. Its planes are 

 vertical, and at its junction with the trap it is moulded to it, but not 

 adherent, and appears to have been formed from rocks at a greater 

 depth than the trap, and ejected through it. The minerals found 

 imbedded in this trap rock are various ; specimens have been obtained 

 of mica, chlorite, felspar, albite, olivine, augite, amphibole, epidote, 

 apatite, adularia, chalcedony, sulphate of lime, probably anhydrite, 

 baryto-calcite, arragonite, calcareous spar, fiuor spar, galena, iron 

 pyrites, sometimes magnetic. Epidote is found also on Mutton Is- 

 land. 



The general mass of this trap rock possesses a hidden nodular 

 structure, only developable by blasting. The nodules consist of pre- 

 cisely the same material as their matrix, and having the same cohe- 

 sion, they cannot be detached by the hammer. 



The nodules are from eighteen inches in diameter to the size of a 

 nut J they are sometimes found pressed together in masses with flat 

 sides, like bubbles. Crystals occurring at the surface of a nodule do 

 not pass into the matrix, but are truncated thereby. In some cases 

 the nodular structure is gradually obliterated, and the usual homo- 

 geneous one replaces it. 



This nodular formation is essentially different from any hitherto 

 described, — as the orbicular granite of Corsica and South of France, 

 the onion stone of the causeway, &c., in which the nodule and the 

 matrix are of different materials. The present structure would appear 

 to have been produced by the ejection of the trap in a fluid state 

 under the sea ; masses of which cooling in their passage fell again 

 into the liquid bed, and being enveloped, were heated nearly to the 

 temperature of the mass, and so adhered without losing their outline. 

 Where several fell together, and were exposed to subsequent pres- 

 sure, they would present the flattened appearance before described ; 

 and when more deeply enveloped, and thus subjected to a higher 

 temperature, the nodular structure would again vanish by their com- 

 plete fusion. 



It is even conceivable that the most capriciously varied parts of 

 this and other trap rocks may owe their origin to the soldering to- 

 gether of nodules of heterogeneous matter, projected from different 

 depths, or at different times, or subjected to successive coolings and 

 heatings. 



Professor Kane read a paper entitled ** Researches on the Com- 

 pounds derived from Pyroacetic Spirit." (Second Series.) 



When dry chlorine gas is passed into pure mesitylene, Cg H4, mu- 

 riatic acid is given off and a compound body, solid, in white prismatic 

 crystals, is formed, giving on analysis the formula Cr, H3 Cl. A yellow 

 substance obtained by the action of iodine on nascent mesitylene, but 

 in too small a quantity for analysis, is considered to be Cg H3 1. 



P2 



