260 THE peesident's addbess. 



most suited for this manufacture is of a soft unctuous character, 

 and useless in its raw state for building purposes ; but when 

 ground up and burnt becomes a most valuable building material, 

 being thoroughly impervious to wet. The natural quality of the 

 stone is such that no admixture of foreign substances is required 

 in preparation for the manufacture, as it contains the necessary 

 ingredients in the proper proportion, and this causes the brick 

 when baked or fused, to become completely vitrified throughout. 



This killas has another recommendation, that the bricks retain 

 their shape during the process of vitrification, while most clay 

 materials when vitrified are apt to swell and bulge out into 

 misshapen forms. When tested by pressure, the vitrified bricks 

 only slightly split at 100 tons pressure, and sustained a thrusting 

 stress of upwards of 400 tons on the square foot. 



The process of making these bricks may be seen at the 

 Phoenix Fire Brick Works, at Grunnislake in this county, where 

 there are at present 6 continuous kilns at work, which have been 

 built on plans patented by Mr. Cowell. Two kinds of brick 

 are there made from the killas, the white vitrified brick, and 

 the blue vitrified brick. 



Through the kindness of Mr. Cowell, and of Mr. T. A. Ellis, 

 the secretary, specimens both of bricks and of the prepared 

 material before it is baked in the kiln, are exhibited here to-day. 



Mr. J. H. Collins kindly supplies me with the following 

 analyses of the two kinds of killas used. 



Silica 



Alumina 



Pei'oxide of Iron .., 



Lime 



Magnesia 



Alkalies 



Moisture and Loss 



100-0 100-0 



Ifanganese Bronze. 



This new alloy, composed of copper, tin, and a little manganese, 

 has been proved by experiments lately made at the Eoyal Gun 

 Factories at Woolwich, to possess great strength and toughness, 



