122 Mr. W. Phillips on some reniatkable Crystals of Quartz, 



the diameter of which from N. to S. is 400 feet lonjr. This 

 is without doubt a crater [caldera) ; and Juarros, although he 

 denies that there are any traces of fire in the water-volcano, 

 describes (tom. ii, p. ^51) it himself exactly as several intelli- 

 gent natives of Guatemala have described it to me. 



North of the group of the volcanos closely ranged between 

 Pacaya and Sunil, at the M'estern extremity of the lake of 

 Atitlan, the heat-exhaling cavern of Central America seems 

 gradually to close. The volcano of Soconusco, of which 

 Juarros makes no mention (in Bauza's chart, 15° 59' lat., and 

 95° 41' long.), is the limit imposed to the series of volcanic 

 eruptions on the western edge of the granitic-gneiss mountain 

 of Oaxada : on the shore of the South Sea there is no volcano 

 for 220 leagues till you arrive at the Volcan de Colonia. After 

 having named, in these pages, between the parallels of 8"^ 50' 

 and 16°, in a direction from S. E. to N.W., five-and-thirty 

 conical mountains, which are considered on the spot as vol- 

 canos, and of which fifteen have undoubtedly emitted smoke 

 or flames within the last half century, I may safely repeat my 

 assertion, — that in no part of the globe, not even in Chili, or 

 the Indian Archipelago and the Alentes, is there so lasting a 

 communication by means of caverns between the interior of 

 the earth and the atmosphere. Future travellers will ascer- 

 tain which among the thirty-five so-called Volcanes de Centro- 

 America are cones of trachyte, and which are real open 

 burninor mountains. 



XXIII. Notice of some remarkable Crystals of Quartz, im- 

 bedded in the Limestone of the Black Rock, near Cork. By 

 W. Phillips, F.L.S. F.G.S. ^-c* 



T LATELY received a letter, dated from Bristol, and signed 

 -*• " Samuel Peter, Dealer in Minerals, &c." accompanied by 

 some specimens of limestone containing prismatic crystals of 

 quartz, terminated at each end by the ordinary pyramid of 

 that substance. These specimens, as the letter informed me, 

 were obtained from a quarry at Black Rock near Cork ; and 

 the writer observed that he sent them on account of the (ap- 

 parently) quartz crystals not having hitherto been publicly 

 noticed, as consisting of alternate concentric layers of quartz 

 and limestone, and that he had sold them under the name of 

 pseudolite, which, however, is not very appropriate. 



These crystals are generally about one-fourth of an inch 

 long, rarely attain half an inch, and their width is mostly equal 

 to about half their length; they are smooth externally for the 



* Communicated by the Author. 



most 



