I 



On the Tertiary Iron Ore Measures. 



157 



and have to be shot or wedged out. The ores also get harder as 

 the roof or perpendicular weight increases ; thus under high 

 escarpments good firm ore is found at five or six fathoms from the 

 outcrop. These are important facts, because at present the best 

 ores may be deteriorated by their fineness, which would pre- 

 vent them being used by themselves in the blast furnace. As 

 the ore from the shallow workings are exhausted and the mines 

 extended into the heart of the mountain, the ore ought to get 

 harder and contain a greater percentage of lumps, thereby 

 enabling it to compete more favourably with the Spanish ores. 



In the present workings the matrix is seldom hard enough to 

 hold the pisolites in position and allow them to be broken across 

 they coming out during the breaking of the ore .; but if the beds 

 are traversed by a dyke (which penetrates the roof) the adjoin- 

 ing portions are baked into a compact mass, and under these 

 circumstances the pisolites break with the matrix. The pisolites 

 vary in size from a shot to that of a hazel nut, while the quality 

 and richness of the ore can be estimated with great accuracy, 

 by observing the size, quantity, and hardness of the pisolites. 

 The pisolitic ore contains from 40 to 70 per cent, of iron, the 

 following being analysis of average samples of Glenariff ore : — 



* A. B. Cowen. t Public Analyst, Wolverhampton. 



X E. W. T. Jones, f.c.s., Wolverhampton, 

 § Ditto, ditto. 



The thickness of the pisolitic ore seam is by no means regular, 

 11 seam of twelve inches may suddenly thicken to twenty-four or 



