1815.] Transactions of the Geological Society, Vol. IT. 59 
of the fineness of a hair, which pass from different parts of each 
of these bodies, and are attached to the surrounding ones; the 
whole of these bodies being thus held in connexion.” He classes 
them among the corals, acknowledging at the same time that they 
bear no resemblance to any known genus. Mr. Conybeare, in 
this paper, shows that they are silicious casts of cavities, which 
have been formed in different kinds of shells by some animalcule, 
which fed upon the substance of the shell, and which, after ex- 
hausting one place, made its way to another. : 
XVI. A Description of the Oxide of Tin, the Production of 
Cornwall; of the primitive Crystal and its Modifications, including 
an Attempt to ascertain with Precision the Admeasurement of the 
Angles by means of the reflecting Goniometer of Dr. Wollaston; 
to which is added a Series of its crystalline Forms and Varieties. 
By Mr. William Philips, M. G. S.—This is a most elaborate and 
exact delineation of all the different crystalline figures which Mr. 
Philips has observed in Cornish tin ore, referred to the primitive 
figure of tin-stoie and twelve modifications of it. But it would 
be impossible to render the paper intelligible to the reader without 
the numerous figures which accompany it, and indeed constitute 
its chief value. The primitive form is an octahedron, consisting 
of two four-sided pyramids applied base to base. The plane 
formed by their junction is a square. ‘The inclination of the faces 
of one pyramid to those of the other is 67° 50’. The twelve mo- 
difications, described by Mr. Philips, consist of the primitive form 
altered by various truncatures, (for the language of Romé de Lisle 
applies best to Mr. P’s mode of describing,) on the angles and 
edges. ‘The figures of the different crystals given by Mr. P. are in 
general very distinct and beautiful. 
XVII. On some new Varieties of Fossil Alcyonia. By Thomas 
Webster, M. G. S.—In the green sand-stone in the Isle of Wight, 
Mr Webster observed numerous bodies exactly resembling the 
branches of trees; in the lime-stone he observed small smooth 
round bodies, bearing a resemblance to eels in motion. These 
bodies occur in prodigious quantities in the romantic cliffs of 
Western Lines. In that place they are found frequently termi- 
nating in bulbous heads, bearing a certain resemblance to a closed 
tulip. He considers them as casts of three or four new and hitherto 
undescribed species of alcyonia. 
XVII. Miscellaneous Remarks accompanying a Catalogue of 
Specimens transmitled to the Geological Society. By Dr. Mac 
culloch.—This long paper consists of remarks on the mineralogical 
Structure of various places in Scotland. The Island of Rona con- 
sists chiefly of gneiss. There are many granite veins in which our 
author observed wolfram. Graphic granite is common, containing 
a mineral which has been termed chalcedony. 1 believe it to be 
rock crystal. Dr. M. makes some remarks on the impropriety of 
applying the term green-stone to primitive transition and floetz 
rocks, His primitive green-stone is obviously syenite, from the 
