James Watt (1736-1819)

Description of a new perspective machine

                    Formation in Brecknockshire.


In common routine, the sequel to the history of a trap for-
mation, should be some attempt to reconcile the appearances I
have described to one or other of the two prevailing theories;
but as I have not the least interest in the inquiry, whether the
earth was formed by fire or by water, I shall abstain from any
discussion on the subject. I would merely wish to observe,
that the hardening of the clay-slate in the neighbourhood of
the trap, and the intermixture of the two formations, may be as
well explained, from the way in which the consolidation took
place, as upon the Huttonian notion of subsequent violence.
I am aware, that the induration of the clay-slate, and the ap-
pearances of disruption in the adjacency of the trap, will be
claimed by the Huttonians, as a fresh verification of their
theory; but the impartial geologist will immediately reflect, that
if the induration of the clay-slate had resulted from the agency
of fire, the same effect ought always to have taken place; but I
have alluded to one spot where the soft clay-slate lies in contact
with the trap. In fact, from any thing I saw to the contrary,
the opposite opinion may be maintained with equal probability,
—that the trap is the more ancient formation,—that the clay-slate
had been deposited around it,—and that the disturbance and
eccentric appearances observable at the foot of the range, were
the effects of a particular kind of attraction in the crystallizing
mass naturally ensuing, where one formation ceased, and ano-
ther began.

There is one fact which will hardly be looked for, according
to either theory. In crossing over from Llandrindod to Bettys,
I found an opening in the very midst of the trap deposit en-
tirely of clay-slate.


ART. VIII.—Description of a New Perspective Machine*. By
the late JAMES WATT, Esq. LL. D. F. R. S. Lond. and
Edin. Member of the National Institute of France, and of
the Batavian Society of Rotterdam.

THE perspective machine was invented about 1765, in conse-
quence of my friend Dr James Lind having brought from In-


* The Editor is in possession of one of these machines, presented to him by
Mr Watt, and constructed by himself.