Page:Proceedings of the Royal Society of London Vol 1.djvu/159

Rh sixteen species of Coluber, and three of the genus Boa, which have these lateral oriﬁces; that they have not as yet been discovered in the genus Anguis ; and that in general it appears that only venomous snakes have this distinctive character.

From Mr. Home’s description and remarks, we learn that these oriﬁces do not lead to the nostril or to the ear, but to a distinct bag of a rounded form, there being within the skull a hollow of the same shape, surrounded by bone, which seems purely intended to receive it. This cavity is described as resembling a cup, formed by the bones of the skull and those of the upper jaw, and not unlike the orbit. The bags bear a relative proportion to the size of the snake; they are, like the eyelids, lined with a cuticle, which forms the transparent cornea, making a part of the outer cuticle; both which, it seems, are shed at the same time.

Mr. Home proceeds next to a description of similar bags in the deer and antelope kinds, which were by some thought to be lachry- mal glands or ducts. 0n close examination, however, it is found that these bags have a secretion of their own, and that there is no reason for thinking that tears ever pass into them, the passage into the nose being unusually free, and the oriﬁces of the bags in general unfavourany situated for the reception of the tears. The use to which the ﬂuid secreted in these bags is applied, is as yet unknown. In the snake this apparatus has that position which seems hest adapted to pour out the ﬂuid upon the cornea when the head of the snake is in an erect position.

The importance of the investigation here entered into,——inasmuch as it applies to most of the operations of nature as well as art,—-appears so manifest, that we shall not recapitulate what the author advances on that subject. Before he proceeds to the detail of his experiments for the purpose of computing the emissions of heat from various bodies under a variety of circumstances, he ﬁnds it necessary to premise a minute description of the principal part of the apparatus he contrived for his purpose. This instrument consists of a hollow cylindrical vessel of brass, four inches long, and as many in diameter, It is closed at both ends; but has at one end a cylindrical neck about eight-tenths of an inch in diameter, by which it is occasionally ﬁlled with water of different temperatures, and through which also a thermometer, constructed for the purpose, is occasionally introduced, in order to ascertain the changes of temperature in the ﬂuid: As it was in the ﬁrst instance only meant to observe the quantity of- heat that escapes through the sides of the vessel, two boxes were contrived, ﬁlled and covered with non-conducting substances, such as eiderdown, fur, &c., which were ﬁtted to the two ends or ﬂat surfaces of