Page:Proceedings of the Royal Society of London Vol 1.djvu/284

Rh but the principal diﬂ‘erence observable is at the pylorus, because, as Mr. Home conceives, some animal substances, after solution, are less readily changed into chyle than others.

In the most perfectly carnimrous animals, the internal membrane is extremely uniform in its appearance; but even in these a division or capability of it by muscular contraction is observable.

The ﬁrst instance in which Mr. Home remarked this division in the human stomach, was in a woman who was burnt to death, after having been unable to take much nourishment for several days before. But since that time, as he has taken frequent opportunities of examining the human stomach recently after death, he ﬁnds that this contraction may generally be met with in a greater or less degree; but when a body is examined as much as twenty-four hours after death, this'appearance is rarely to be met with; which accounts for its not having been before particularly noticed.

The series of stomachs arranged according to their structure, which has been given, includes the principal peculiarities that appear to Mr. Home capable of inﬂuencing the process of digestion: it is, however, considered only as a ﬁrst imperfect attempt, which he hopes that other inquirers will render more complete.

The account, given by Sir Isaac Newton, of these coloured arcs. appeared to Dr. Herschel highly interesting, but he was not satisﬁed with the explanation of them. Sir Isaac Newton accounts for the production of the rings, by ascribing to the rays of light certain ﬁts of easy transmission and alternate reﬂection; but this hypothesis seemed not easily to be reconciled with the minuteness and extreme velocity of the particles of light.

With the view of inquiring ﬁnther into the cause of these pheno- mena, Dr. Herschel, so long since as the year 1792, borrowed of this Society the two object-glasses of Huygens, one of 122, and the other of 170 feet focal length. Notwithstanding various interruptions, the series of experiments, made in the course of this time, has been car- ried to a considerable extent; and Dr. Herschel thinks the conclu- sions that may be drawn from them, sufﬁciently well supported to point out several modiﬁcations of light that have been totally over- looked, and others that have not been properly discriminated.

The aim of the present paper is to arrange the variom modiﬁca- tions of light in a clear and perspicuous order; but Dr. Herschel re- serves his sentiments upon the cause of' the formation of concentric rings, for a subsequent communication.

The ﬁrst section describes diﬂ‘erent methods of making one set of concentric rings visible. The, ﬁrst method consisted in placing a double convex lens, of 26 inches focus, upon a piece of glass, of which