602 



which I was previously acquainted, that I was induced to 

 submit it to analysis. It occurs in the locality already men- 

 tioned, at Rowry, a httle to the east of Glandore, in lumps" 

 of variable size, which, when broken, exhibit, though but iVt 

 developed, the faces of crystals belonging apparently to the 

 right prismatic system, mixed, however, here and there with 

 what would appear to be a brown haematite. Some of the 

 crystalline portion of the ore, very carefully selected, gave, 

 upon analysis, the following constituents : 



(1) (2) 



Silex 3.08 



Perox. Iron 34.88 0.436 20 



Red Ox. Mangan. 50.67 \ _Sesquioxide 5.25 0.066 3 



Oxygen . . . 6.52) Peroxide 51.94 1.188 54 



Water 4.85 0.539 24 



100.00 

 These results do not conduct to any very probable formula. 

 But if we suppose that what is set down as sesquioxide is 

 really present as peroxide, a supposition which accords 

 sufficiently well with the analysis, then the composition of 

 this ore becomes very simple, being represented by the 

 formula Fra O3, HO +3 Mn O2, that is by one identical with 

 that which we have found for the psilomelane, when we 

 substitute sesquioxide of iron for the sesquioxide of man- 

 ganese. I have no doubt that this represents its real 

 constitution, so that it may be safely set down as a new 

 and very distinct species. I may observe that this mineral 

 answers well for yielding oxygen, but is uneconomical as a 

 source of chlorine, in consequence of the wasteful consump- 

 tion of acid, in order to the saturation of the peroxide of 

 iron ; one-half in fact of the acid is uselessly expended. 



Mr. William Andrews, Secretary to the Dublin Natural 

 History Society, read a paper upon the genera of Ferns 



