C 3*3 3 
XXIV. Experiments and observations on the Newry pitch-stone, 
and its products, and on the formation of pumice. By the Right 
Honourable George Knox, F. R. S. 
Read May 9, 1822. 
The locality of this mineral, and the singularity of its ex- 
ternal characters, having excited my curiosity, I took advan- 
tage of the facilities furnished by the liberality of the Royal 
Society of Dublin, of which I have the honour of being one 
of the Vice Presidents, to make the subjoined analysis in their 
laboratory. 
Doctor Fitton, in an excellent paper inserted in the first 
volume of the Transactions of the Geological Society, has 
given a minute description of the site and external characters 
of the Newry pitch-stone. I shall transcribe it, previous to 
laying before the Royal Society my own observations. I do 
so with more satisfaction, as we in general agree ; in fact, 
scarcely two specimens are exactly the same, although con- 
tiguous to each other in the vein ; some being compact, some 
thin slaty, some olive, and some leek-green ; some so disin- 
tegrated, particularly when exposed to the air, as to be friable 
between the fingers, while others retain their gloss, consis- 
tency, and colour, with much tenacity, although they all fall 
at length into rhomboidal fragments. I may add also, that 
while some are quite porphyritic, others have but a few specks 
of felspar on their surface. 
MDCCCXXII. S S 
