718 Proceedings of the Royal Irish Academy. 



tlie possibility of a few layers of it in stalactites, had it ever been lielcl 

 largely in solution. At any rate, the drippings, which would under 

 such a supposition be charged with carbonate of magnesia, falling on 

 the floor, say of a cave, if they produced any stalagmite, should pro- 

 duce a magnesian one, or one containing a very considerable propor- 

 tion of that body. It appears, however, that neither the one nor the 

 other contains any appreciable amount of it at all, and even those 

 from magnesian limestones follow the general rule. I can hardly 

 think that, in the case of stalagmites, some of the magnesian carbonate, 

 if it had been present in the solution which formed them, would not 

 remain. It ought, certainly, to be found in the upper layers, as sta- 

 lagmite is by no means porous, but this seems not to be so. I am 

 speaking now of stalagmite formed in places where the water could 

 have had no ready means of escape except evaporation. 



On the other hand, the argument as to the most soluble being 

 carried away entirely ought to hold good as respects the carbonates of 

 lime and iron. As the latter is least soluble of all, whenever it occurs 

 in stalactites they should consist nearly entirely of it, if the above 

 idea were correct. A great amount of the more soluble lime-salt 

 would be carried off while the carbonate of iron was crystallisingv 

 and we would have stalactites containing usually a very large per- 

 centage of iron ; but this is rarely the case. 



As analyses of stalactitic bodies are not numerous, I give those of 

 two or three which I have examined. 



No. I. — Stalagmite — from the floor of Dunmore Cave, Co. Kil- 

 kenny. 



A part of the upper layers where the thickness was at least 

 6 inches. 



Anaitsis. 



Carbonate of lime, 97-12 



,, magnesia, 0-79 



,, iron, ....... 1-86 



Peroxide of iron, alumina, .... 0-23 



100-00 



This stalagmite was of a dirty grey colour, and apparently full of 

 impurities. 



IS'o. II. — Stalagmite from roof breccia of the Shandon Cave, Dun- 

 garvan : — 



This stalagmite forms an extremely pretty mass, of a clear cream- 

 colour, and is well crystallized. It occurs in large quantity, and often 

 in considerable masses amongst and underneath the breccia. The spe- 

 cimens examined adhered to the under side of the limestone, a portion 

 of which was analysed and experimented on. (See Experiments 

 4 and 5.) It is therefore reasonable to suppose that its materials 

 were derived from that very magnesian rock. 



