\ 
226 Dr. Cooper on Volcanoes 
Clinkstone passing into trap porphyry in Sky. 3 Geol. 
trans. 66. Basalt passing into porphyry. Ib. 80, 189, 191, 
192. , 
Porphyritie volcanic mountains, noticed by M. Arduini 
in the Vincentin territory ; at Bresciano, and at Bergames- 
co. They repose on slate. Ferb. tr. 37. Porphyritic vol- 
canic hills between Walshonickel and Newmack. Ib. 325. 
They continue to Brandsol, and split into prismatic and co- 
lumnar forms. Ib. hy 
The porphyry called Serpentino, verde antico, found in 
large blocks near Ostia, where the Egyptian ships used t 
unload, contains cells filled with agate. Ib. 225. 
Trappean porphyries intimately connected with volcanic 
productions. 1 Humb. pers. narr. 94, 212. Clinkstone 
porphyry covers the basalt of the Bohemian volcanic moun- 
tains. Ib. 211. Amygdaloid covers the basalt, at La Pun- 
ta di Nager at Teneriffe. Ib. 214. The Lava in the plain 
of Retama at Teneriffe, very similar to the resinite porphy- 
ry of Tribrick in Saxony. Ib. 215. The porous basalt of 
the Island of Gratiosa, passes into Amygdaloid or Mandel- 
stein, according to Humb. I. 91. 
Pitchstone Lavas, near Teols: and Bajamonte. 3 Spal. 
tr. 250, 251. 
Porphyry with agate opal. Brande’s Catal. p. 171, 179. 
As to the Amygdaloids of this formation, we can ac- 
count for their cells and pores, only as we account for the 
cellsand pores of Lava and other igneous stones ; and for 
the agates, quartz, carbonate of lime, prehnite and zeolyte 
found in them, as we account for the same substances found 
under like circumstances : in volcanic amygdaloids : for in 
no case can we legitimately reason to a disputed subject, 
but from what we know of similar circumstances undisputed. 
Hence then it appears, that the Porphyries, the Green- 
stones, the Amygdaloids and the Pitchstones, are equally 
common to known volcanic formations, and to the rocks 
now considered. Fora further consideration of the gene- 
ral fact, and of the reasoning here adopted, I refer to Dr. 
McCulloch’s paper on the Granite of Aberdeenshire, in No. 
19 of Brande’s Journal. 
I have next to shew that the other acknowledged charac- 
ters of Lava, belong in an equal degree to the Basalt of the 
F'leetz trap formation. 
