916 STONE, ARTIFICIAL 



In attempting, however, to carry out this plan, Mr. Kansome found that two diffi- 

 culties of a rather formidable character presented themselves. It was found that, 

 in the process of desiccation, the surface of the stone parted with the moisture 

 contained in the soluble silicate, and became hardened into a tough impervious 

 coating, which preA T ented the moisture escaping from the interior of the mass. Any 

 attempt to dislodge the water retained in combination with the silicate in the interior 

 of the stone, by raising the temperature of the whole above 212, had merely 

 the effect of breaking this outer skin of desiccated silicate, and rendering the surface 

 cracked and uneven. 



Instead, therefore, of allowing the stones to be dried in an open kiln, they were 

 placed in a closed chamber or boiler, surrounded with a steam-jacket, by which the 

 temperature of the interior chamber could be regulated. In order that no superficial 

 evaporation should take place while the stones were being raised to the temperature 

 of the steam in the jacket, a small jet of steam was allowed to flow into the chamber, 

 and condense among and on the surface of the goods ; until, as the temperature of the 

 interior of the stones rose to 212 and upwards, they became enveloped in an atmo- 

 sphere of steam, which effectually prevented any hardening of the surface. The 

 minute vents or spiracles formed by the steam as it was generated in the interior of 

 the masses, remained open, when the vapour contained in the closed chamber was 

 allowed slowly to escape, and afforded a means of egress to any moisture which might 

 still be retained among the particles of sand and cement. The whole of the moisture 

 contained in the silicate of soda having been thus vaporised before it left the stone, an 

 opportunity was afforded it by opening a communication with the external atmosphere, 

 to pass off, leaving the interior of the stone perfectly dry. Simple as this arrangement 

 may seem, we will venture to say that not one of our readers has hit upon the expedient 

 through his own cogitations on the subject. 



The process, in effect, consists in stewing the stones in a closed vessel, and when all 

 the moisture which they contain is converted into vapour, allowing it to escape, so 

 that no one part of the mass can be dried before another. By this means Mr. Ransomo 

 was enabled to desiccate his artificial stone without any risk of the cracking or 

 warping which had hitherto been the result of his attempts to harden them by exposure 

 in an open stove. 



After being thoroughly dried they are taken to the kiln, but, instead of being placed 

 in seggars or boxes of clay, as is usually done in the potter's kiln, the goods are first 

 bedded up with dry sand, to prevent any risk of their bending or losing their shape 

 while burning. Flat slabs of fire-clay are then used to separate the varioxis pieces 

 laterally, and similar slabs are placed over them to form a shelf, on which another 

 tier of goods is placed. The temperature of the kiln is very gradually raised for the 

 first twenty-four hours ; the intensity is then augmented until at the end of forty-eight 

 hours a bright red heat is attained, when the kiln is allowed to cool gradually, for four 

 or five days, when the goods are ready to be taken out. 



From being composed almost entirely of pure siliceous matter, this artificial 

 stone is not acted upon by acids, and is apparently quite insoluble, even in boiling 

 water. 



By proportioning the amount of cement, and varying the character of the sand 

 which enters into the composition of the stone, it can be made porous or non-porous, as 

 may be desired. The average absorbent power of artificial sandstone is less than that 

 of the Bolsover Moor Dolomite used in the erection of the Houses of Parliament, and 

 a little more than that of the Cragloith Sandstone. 



An improvement in the manufacture of Hansome's Stone, or, as it is sometimes 

 called Aptsnite, was made and patented by the inventor in 1872. 



It was found in practice that the process of washing the Ransome stone so as to 

 completely remove all traces of the chloride of sodium, from large masses was open to 

 objection ; it was both tedious and expensive, especially in localities where there was a 

 difficulty in obtaining a good supply of water at a reasonable cost, besides which in 

 producing so large an amount of chloride of sodium which had afterwards to be re- 

 moved as a waste product at a considerable cost. The bulk of the alkali, which was 

 by far the most expensive ingredient in its composition, was ejected instead of being 

 utilised, for still further increasing the density, strength, and hardness of the stone. 

 Some years since a siliceous deposit was discovered at the base of the Chalk Hills in 

 Surrey, possessing some very peculiar properties, amongst others, that of being readily 

 soluble in a solution of caustic soda or potash at a moderately low temperature. Messrs. 

 Paine and Way, in the 12th volume of the Journal of the Royal Agricultural Society, 

 in a paper entitled ' On the Strata of the Chalk Formation,' thus describes the soluble 

 silica deposit: 'Immediately above the gault, with the upper member of which it 

 insensibly intermingles, lies a soft white-brown rock, having the appearance of a rich 

 limestone. It is very remarkable on account of its low specific gravity, and still more 



