196 Mr. G. P. Serope on the Formation of Craters, 
1826-27, will be evident to any one who will take the trouble 
to refer to those works. 
It is not, however, for the vain purpose of claiming a priority 
in these views that I now ask the attention of the Society to 
them, but because the subject has not, I think, yet attained the 
consideration it deserves from the geologists of this country ; 
and especially because of its leading, if followed out, to further 
inferences of considerable importance, which were hkewise sug- 
gested by me in 1825, but have been hitherto only partially 
pursued to their legitimate consequences. 
Laminated or schistose rocks, slaty cleavage, and folded rocks.— 
I refer to the mechanical changes in the texture and structure 
of the plutonic rocks which could not fail to have resulted from 
the mutual friction of the component crystalline particles attend- 
ant on their internal movements, whether caused by mere dila- 
tation and recompression in place, or by a shifting of the entire 
mass in any direction, under intense and opposite, but irregular 
pressures. 
I was led to reflect on this by observation of the ribboned 
pitchstones of Ponza and Ischia, in which, while in a state of 
vitreous fusion, crystallites had formed (just like those of the 
Oldbury obsidian), and subsequently been broken up by the 
movement of the semi-liquid mass, and drawn out into long 
stripes, giving a ribboned appearance to the rock. 
Further examination proved to me that the ribboned trachytes 
of Ponza and Ischia, and some ribboned clinkstones, owed that 
character to a similar elongation of the felspar crystals and fels- 
pathic particles which they previously contained, in the direction 
in which the semi-liquid mass flowed, or rather was forced to 
move, and in which the pores or cells, when there are any, are 
equally elongated. These observations suggested to my mind 
the reflection, that the solid particles of any crystalline rock 
which is put in motion while in a state of imperfect solidity, and 
under the influence of opposing pressures, must be subject to a 
great amount of mutual friction or disturbance, by which their 
final arrangement when wholly consolidated will be determined. 
Thus, suppose a mass of granite, of which A B (fig. 4) repre- 
sents the section, consisting of crystals of felspar and mica irre- 
gularly disposed in a basis of more or less liquefied or gelatinous 
silex, exposed to movement in the direction AB, while under 
vast pressure both from above and below, that is, in the oppo- 
site directions C and J). Whether the surface C or D, or both, 
remained fixed, or merely moved, owing to resistances, at a 
slower rate than the other parts, the crystals in the latter would 
be turned round by internal friction, and rearranged and drawn 
out in stripes or planes in the direction of the motion, while the 
