igneous Origin of some Trap Rocks. 127 
pearance that has been described, and it extends up much higher than 
in the general mass, and is visible for some distance inward, from the 
contiguous surfaces of the masses of rock, penetrating into their sub- 
stance. Ina few places, the inflation of the trap rock continues high- 
er than has been described in the general statement; it seems as if 
the force which produced the effect, suddenly hove up a wave, until 
it was repressed by superincumbent pressure, and again subsided to 
the general level. Perhaps it would imply too much of hypothesis, 
if we were to say that this arose from the mass above being less 
heavy, as the superincumbent trap appeared in.such places generally 
thinner; but it was not always so in appearance, for there were 
places where the trap was only a few feet in thickness, and the in- 
flation was not always increased.* 
What is the impression which these remarkable appearances must 
make upon a common mind of good intelligence? Some of the spe- 
cimens, both of the altered sandstones and traps, were exhibited to 
such persons, and without imparting to them any hint of their suppos- 
ed origin, they were asked what gave those stones that appearance ? 
the answer was, they have been in a furnace, and the different va- 
rieties have been subjected to different degrees of heat. > 
Such are the impressions of all who view the specimens, and it is 
decisive that they are of a very indubitable character, because all agree 
in their opinion of them, whether interested in such subjects, or in- 
formed in geological facts and theories, or not. For myself, I must 
say, that the effects that have been produced, both upon the trap ai 
sandstone, which are so distinctly and strikingly visible for an average 
depth of seven or eight feet, and in some places more, and fora 
continued distance of nearly a mile, are such as I can attribute to no 
agent but fire. That there was a great and pervading eause, which 
operated upon both rocks at their junction, cannot be doubted ; that 
this cause was resident in the trap, seems almost equally certain, be- 
* It does by no means, however, follow, that this was the original condition of the 
trap; the contrary is perhaps highly probable : that is to say, that there was origi- 
nally a much thicker mass, either of trap or other matter, above the whole of that 
which we now see, and that in the progress of ages, it has been removed by the 
operation of both gradual and violent causes, : 2 = 
t in my last visit to this place, I was in company with several highly intelligent 
gentlemen, and in a former one, with ladies of a similar character, and the impres- 
sion made upon them all, was the same. I found it even among the workmen in 
the enarry. 
