248 ANNUAL OF SCIENTIFIC DISCOVERY. 



proved entirely satisfactory. Indeed, hasty fixation can hardly be 

 compatible with tenacity and permanence, and it is probable that the 

 best effect would be attained by using a silicate alone, many times, 

 and at distant intervals. 



With regard to stone, silicatization is of little importance in this 

 country, as we have few varieties that need artificial hardening. But 

 in some places there is a lack of good clay for brick-making, and 

 such earth as is worked gives very tender, absorbent brick, ill calcu- 

 lated to bear handling and exposure to the weather. In many cases 

 it would doubtless be advantageous to silicatize the exposed surface 

 of the bricks after they have been laid. This is deserving of especial 

 consideration where they are subjected to the action of sea-water, 

 which is particularly destructive of porous building materials. 



Wageninann succeeded in making artificial meerschaum by mixing 

 water-glass, lime, magnesia, and carbonate of magnesia, and simply 

 drying. 



Considered merely with regard to its mechanical properties, water- 

 glass would appear very suitable to replace starch and glue as a 

 glazing material, in many cases. In fact it was brought forward by 

 Leigh, a year or two ago, as a substitute for starch in sizing cotton- 

 yarn for weaving, and in putting the final finish on cotton fabrics. 

 But its chemical character indicates its unfitness for such uses. 

 Starch, after drying, remains unchanged itself, and has no action on 

 the stuffs; while a silicate is altered by exposure to the air, and 

 loses its smoothness as well as much of its rigidity. Besides this, it 

 is alkaline, and therefore tends to weaken the fibre, an effect which 

 becomes at once apparent when water-glass is used strong for pro- 

 ducing very stiff fabrics. 



Silicate of soda, on account of its chemical relations, has come into 

 general use as a substitute for phosphate or arseniate of soda in dung- 

 ing printed calicoes. This, the most important of all the applica- 

 tions, was patented in England by Jager in 1852, and it has now 

 almost entirely superseded other dunging materials. 



* 

 PRESERVATION OF STONE BY THE PROCESS OF SILICIFICA- 



TION. 



The difficulty which besets many of the processes of silicification is, 

 that along with the needful silica so much superfluous, and indeed 

 injurious, matter is introduced that the valuable qualities of the silica 

 are in a great measure counteracted, the disintegration of the stone 

 being sometimes actually caused by the efflorescence of these extra- 

 neous substances ; the porous character necessarily induced as the 

 consequence of the gradual removal of the soluble salts in juxtaposition 

 with the silica almost undoing the binding and hardening action of this 

 valuable material. Silica can, however, be obtained in the form of 

 pure aqueous solution in several ways : 



1. By dissolving sulphide of silicium in water, when sulphuretted 

 hydrogen is given off, and the silica remains completely dissolved, 

 and in such quantity that the liquid gelatinizes when an attempt is 

 made to evaporate it. 



2. By precipitating silica in the gelatinous state from an alkaline 



