Mr. G. H. Fielding on a new Membrane of the Eye. 87 



Strontianite. — The Arragonite of the Causeway contains a small portion of 

 Strontian. 



Alum.— Occurs efflorescent on the Slate Clay of the Lias formation at 

 White Head near Carrickfergus ; also at Coal Island, Derry: GieseckS. 



Aluminite. — In Trap at Gerron Point and Portrush. 



Copper Pyrites. — With Galena, Newtonards, Down. 



Iron Pyrites. — Abounds in Trap and other rocks. 



Magnetic Iron Ore. — Occurs in great abundance in Trap at Portmuck, 

 Island Magee, where it was first found by my friend Mr. M'Adam ; it 

 is crystallized in octahedrons ; lustre splendent. 



Specular Iron. — Not uncommon in our Trap Rocks, crystallized in rhom- 

 boids. 



Micaceous Iron Ore — In several places in Mourne Mountains. Anhydrous 

 Bisilicate and anhydrous Disilicate of Iron have been found in Mourne 

 by Mr. P. Doran, and recognised by Dr. Thomson. Red Hamaetite, 

 Clay Iron Stone, and Bog Iron Ore are met with in several places. 



Galena and Green Phosphate of Lead. — Occur in the Newtonards lead 

 mines, Down. 



Radiated Gray Antimony. — Said by Sir C. Giesecke" to occur near London- 

 derry. 



Itutile. — Occurs in Quartz in Mourne. 



Coal. — Its different varieties are common. 



Amber. — Said to occur in the Coal of Rathlin, in small bits. 



Belfast Academy, Feb. 12, 1833. 



XV. On certain Changes of Colour, induced by chemical and 

 other Agents, in the Membrane lining the Choroid Coat of 

 the Eye ; in Reply to an Editorial Note in Lond. and Edin. 

 Phil. Mag. and Journ., vol. i. p. 115. By G. H. Fielding, 

 Esq. M.B.C.S. Curator of Comparative Anatomy to the Hull 

 Literary and Philosophical Society. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



[ BEG leave to send you the following reply to a note ap- 

 *• pended by you, to a communication of mine in vol. i. 

 page 115. of your New Series. For that note I feel much 

 obliged to you ; inasmuch as it led to further investigation, 

 and to another entirely novel, and I think decisive experiment 

 on the point. I am, Gentlemen, Your obedient Servant, 



Geo. H. Fielding. 

 The part of my communication to which your remarks ap- 

 ply is the following : " 6thly. It is possible by chemical agents 

 (which, according to Bichat, have not the slightest effect on 

 the pigmentum of the eye) to destroy and restore these colours 

 at pleasure. Take a section of a beast's eye in which the co- 

 lours are vivid, and dip it into any dilute acid (nitric, muriatic 

 or sulphuric), you will perceive the colours immediately begin 



