186 NOTES ON HYDRAULIC LIME AND CEMENT. — MASON. 



" It will be noted from the analysis that the stone contains 

 84.82 per cent, of lime, which is too high for a natural cement. 

 It therefore becomes necessary to employ with it clay of a suit- 

 able character, and there should be. occurring between the 

 layers of this stone, five or six clays of the requisite composition. 

 This material, in common with the British Lias limestones, 

 varies in composition in piece and piece, in this case the varia- 

 tion being, on the sample submitted, from 4 to 5 per cent, of 

 carbonate of lime. 



" In dealing with the production of cement from this material, 

 therefore, it will be necessary to employ great care in the 

 adjustment of the proportions of the stone and clay, which could 

 only be done by the employment of a skilled chemist. 



" The stone is readily pulverized, and it may be as well to 

 point out that owing to the natural inter-mixture with it of a 

 proportion of silicates of iron and alumina, or clay, it is not 

 necessary to reduce it to nearly the same fineness as when deal- 

 ing with Thames or Medway chalk, which is practically pure 

 carbonate of lime. 



" For the purpose of practically demonstrating the value of 

 the stone as a material suitable for cement making, I have pre- 

 pared some samples of cement from it, with the admixture of 

 the necessary proportion of Medway clay. The following repre- 

 sents the composition of the clay used : — 



Loss at red heat (organic) 5.89 per cent. 



Silica ...... : .'. 62.41 



Alumina 18.09 " 



Ferric oxide 10.35 " 



Carbonate of lime 1.63 " 



Alkalies 2.10 



Loss ■ .03 



100.00 



