Kirwanian Society of Dublin. 399 



formation with the containing rock, occur not unfreqnently. 

 It has not been fully ascertained whether the pitchstone 

 and pearlstone porphyries occur in beds or veins, but the 

 former appears the more probable. The top of Cairnairney- 

 hill at Sandy Braes, and of Courtmartin, Tiveraw, and the 

 Knockins at Newton Glens, Dr. O. considers as the newer 

 beds or deposits which remain, of this formation. A re- 

 mark which appears to merit attention, was made respecting 

 the quartz and felspar crystals which occur in these por- 

 phyries. The felspar in particular has considerable lustre, 

 hardness, and 1-egularity, and may he considered as the 

 glassy subspecies of Werner, in the newer beds of this for- 

 mation as at the top of Cairnairney, while these characters 

 in general diminish the nearer we approach to what are 

 considered the mechanical deposits, or the older beds of the 

 series. The paper concluded with some theoretical remarks 

 relative to the geognostic situation and mode of formation 

 of porphyry. Jf the trap rocks of Antrim belong, as is 

 coiwrnonly supposed, to the newest floslz formation of 

 Werner's arrangement, it will then follow that this por- 

 phyry is newer than any hitherto observed by Professor 

 Jameson, "and will probably hold a place in the system un- 

 der the name of the Newest Floetz Porphyry. The answer 

 to Mr. Jameson's query respecting the peaHstone of Sandy 

 Braes will be then obvious. 



At the fourth meeting held on the 20th, Dr. Ogilby 

 submitted to the Society some remarks upon Mr. Davy's 

 late proposal of rejecting the oxymuriate oi" lime from the 

 process of bleaching, and substituting the oxymuriate of 

 magnesia, and he presented the results of several experi- 

 ments upon this subject. 



After some observations upon Mr. Davy's notion that 

 the residual muriate of lime, which rennins in solution 

 after the usual process of steeping in the oxymuriate, pos- 

 sessed a caustic property and destroyed the fibres of the 

 cloth, it was argued that the singular mode of reasoning 

 on' the asseriion made use of by Mr. Davy, " that if a 

 strong solutio!! of muriate of lime rendered the cloth un- 

 sound, a \^eak one ought to be proportionally detrimental," 

 could not be for a moment attended to by the bleacher, 

 without rejecting every article essential to his process, as 

 potash, sulphuric acid, &c. which in their concentrated 

 state will dissolve or burn the cloth. Notwithstanding, 

 however, that Mr. Davy had been guided in making his 

 new proposal by views of ihe subject altogether erroneous, 

 the action of nuiriate of lime on linen clplh was deemed 



C c 4 worthy 



