Transactions of the Royal Society of Edmhurgh. 347 
in the cavities of minerals and artificial crystals, the author de- 
scribes seventeen specimens of minerals and artificial crystals 
which contain cavities generally filled with water. One of the 
finest of these specimens is from the cabinet of Mr Thomson of 
Forth Street, and which originally belonged to the King of 
Kandy. Besides an aqueous fluid, the cavity contains several 
pieces of opaque solid matter, which, with a little management, 
may be seen falling from one side of it to the other. The par- 
ticular descriptions contained in this section, can only be under- 
stood from the drawings which accompany the paper. 
2. Ohservatiofns on the Comparative Anatomy of the Eye, By 
Robert Knox, M. D. Member of the Wernerian Society, 
and of the Medico-Chirurgical Society of Edinburgh.—* 
P. 43-78. 
An abstract of this paper is given in the present Number of 
this Journal, p. 338. 
3. Notice of an undescribed Vitrified Fort, in the Burnt Isles, 
in the Kyles of Bute, By James Smith, Esq. of Jordan- 
hall, F. R. S. E.— P. 79->81. 
This fort occurs on the most northerly of the Burnt Isles of 
the Kyles of Bute. The island is a flat gneiss rock, with about 
half an acre of vegetable soil on its summit. The fort stands on 
the southern or highest extremity, and is only twelve or fifteen 
feet above high-water mark. The walls form a circle, or rather 
an irregular polygon, about sixty-five feet in diameter, and oc- 
cupy nearly the whole of the liighest end of the island. Mr 
Smith traced the vitrified matter all round, and is of opinion: 
that the walls were originally about five feet thick. They ap- 
peared to him to be entirely composed of the gneiss, which, 
forms the rock of this and the neighbouring islands. Some 
of the stones are slightly glazed, whilst in others the fel- 
spar appears to be converted into a dark brown glass, either 
run into considerable masses, or into veins alternating with the 
strata of quartz, which has become granular like freestone. The 
vitrified matter sometimes forms a white enamel. Mr Smith is of 
opinion, that these buildings were probably constructed at a pe- 
