228 



On the Silica Strata of the Lower Chalk. 



2nd. Flint, which does not dissolve to any considerable extent 

 in boiling alkalies at the ordinary temperature, but which can be 

 made to dissolve in such solutions when by means of a steam- 

 tight boiler a temperature of about 300° Fahr. is obtained. And 



3rd. Quartz rock or sand, which will dissolve neither in the 

 one case nor the other. 



Up to this time, although familiar enough with the two latter 

 forms of silica, we have only known the first as an artificial pro- 

 duction, derived in fact by chemical processes from one of these. 

 It has not been known to exist in any quantity as a natural pro- 

 duct. It is well, by the way, before leaving this part of the 

 subject, to explain to our agricultural readers that, although clay 

 contains silica, and this silica is in combination with alumina, and 

 may, by certain treatment, be separated from the alumina in the 

 soluble condition, it does not exist in the clay in that condition 

 and cannot be employed as a source of soluble silica. Caustic 

 alkalies dissolve out from clay a small portion of silica, seldom, 

 however, amounting to more than 1 or 2 per cent. ; the great 

 bulk of the clay remains unacted on until by digestion with acids 

 a separation is effected between the alumina and silica, when the 

 latter becomes soluble in alkalies and is then in the chemically 

 active state. We hope that this explanation will be sufficiently 

 clear and explicit to enable our readers to understand that, 

 although silica is abundant enough on the surface and in the 

 bowels of the earth, soluble or chemically active silica, as 

 described by us, has been hitherto unknown, except as an arti- 

 ficial product. 



It is our pleasure to lay open to all whom it may benefit an 

 abundant and accessible source of this substance ; and inasmuch 

 as a new material will very soon find numerous and important 

 applications, so a modification of a substance already well known, 

 but which by such modifications becomes in fact a new substance, 

 offers to those who will rightly employ it, opportunities of accom- 

 plishing that, which before its discovery would have been 

 impossible or impracticable. 



It is difficult, therefore, to say what may or may not be the 

 use in the arts to which this new substance may be applied, but 

 we shall here confine ourselves to the endeavour of showing that 

 to agriculture it may probably become eminently serviceable. 



Whilst, however, we are justified in claiming for ourselves the 

 merit of having been the first to discover and to examine the 

 beds of soluble silica as they exist in England, and still further 

 to point out the peculiarities of this deposit and the uses to which 

 it might be put, especially in agriculture, it is right that we 

 should state that when our investigation was well nigh complete 

 our attention was drawn to a notice of a similar deposit existing 



