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. 
Porphyritic 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- 
eanic hills between Walshonickel and Newmack. Ib. 325. 
They continue to Brandsol, and split into prismatic and co- 
lumnar forms. Ib. 
The porphyry called Serpentino, verde antico, found in 
large blocks near Ostia, where the Egyptian ships used to 
unload, contains cells filled with agate. Ib. 225. 
rappean 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. For a 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 
Fleetz trap formation. 
