VIII. A Geological Description of Glen Tilt.
By john Mac Culloch, M.D. F.L.S. President of the Geological Society,
Chemist to the Ordnance, and Lecturer on Chemistry at the Royal
Military Academy at Woolwich.
It is well known that the appearance of the granite in various
parts of the valley of the Tilt afforded to Dr. Hutton one of the
original arguments on which his theory was founded. Hence
this spot has acquired among geologists a sort of classical celebrity,
sufficient to render it an object of interest, independently of that
which is excited by the intricate and remarkable disposition of its
rocks. Observations, now more numerous than in his day, have
brought to light so many facts similar to those which appeared to
him so important, that there is no difficulty in pointing out abundant
instances of an occurrence once supposed rare. But having
had occasion while examining these rocks to observe other interesting
appearances, which have been either misapprehended or overlooked,
I consider that a notice of them will not be unacceptable
to the Society. The notice is accompanied by such specimens and
drawings as are requisite for the illustration of the subject.
In describing Glen Tilt I have been under the necessity of differing on certain points from those who have preceded me. An examination of many of these points of difference would lead to discussions as endless as they would be fruitless, and give this
