STONE, ARTIFICIAL 917 



so considering its position, by reason of the very small quantity of carbonate of lime 



which it contains. It is one of the richest subsoils of the whole chalk series, being 



admirably adapted for the growth of hops, wheat, beans, &c. 



' The section of rock at Farnham is about 40 feet in thickness. The analysis gives 



as follows : 



Per cent. 



Combined water and a little organic matter . . . 4-15 

 Soluble in dilute acids, 57' 10 : 



Silicic acid (silica) 46'28 



Carbonic acid none. 



Sulphuric acid . , trace. 



Phosphoric acid ........ ditto. 



Chlorine none. 



Lime 0'26 



Magnesia '07 



Potash -79 



Soda -43 



Protoxide and peroxide of iron . . . . . 6'12 



Alumina . . . . . . . . 3 - 15 



Insoluble in acids, 38'75 : 



Lime 2-91 



Magnesia traces. 



Potash 1-51 



Soda -60 



Alumina, with a little oxide of iron 14'20 



Silicic acid and sand 19'59 



100-00' 



The same authors contributed another article to the 14th volume of the ' Journal,' 

 on ' the Silica Strata of the Lower Chalk,' in which they state that ' when the 

 former paper was published, they were not unaware that this stratum contained a large 

 proportion of silica in the form which chemists call " soluble ; " but that they wished, 

 before making public their discovery, to ascertain whether it existed in sufficient quan- 

 tity to render it available for agricultural use.' They then detail the result of their 

 researches during the intervening two years, as far as they concern agriculture, men- 

 tioning all the localities in which this stratum may be found in England, and the 

 various ways of employing it beneficially as a manure. They allude to the fact that 

 it will be found useful in its application to the arts. 



Taking advantage of this peculiarity, Mr. Eansome commenced a series of experi- 

 ments,, in order to determine if it were possible without the use of chloride of calcium, 

 to produce a stone in all respects equal in quality to what had hitherto been made, 

 and in this he succeeded. By mixing, in lieu of the chloride of calcium, suitable 

 quantities of lime, (or substances containing lime), and- the natural soluble silica above 

 alluded -to, with sand and a solution of silicate of soda or potash, which when intim- 

 ately incorporated are moulded in the usual way, and allowed to harden gradually, as 

 silicate of lime is formed by the decomposition of alkaline silicate produced by the 

 action of the lime, the mass becomes thoroughly indurated, and in a very short time 

 is converted into a very compact stone, capable of sustaining extraordinary pressure, 

 and increasing in strength and hardness with age. Upon this improvement, Dr. T. Sterry 

 Hunt makes the following remarks : After expressing his satisfaction at the beautiful 

 results arrived at by Mr. Eansome, who after years of experiment, had solved satis- 

 factorily and completely a great industrial problem, he stated that he had followed 

 with the more interest the labours of Mr. Eansome during many years, from the fact 

 that he himself had formerly carried on, in 1857-58, a series of experiments very 

 similar in character and in chemical results, in his endeavours to find out the method 

 by which certain soft earthy rocks, consisting in great part of silica and carbonate of 

 lime, have become hard and crystalline. Dr. Sterry Hunt had shown by researches in 

 the laboratory, and also by observations of limestone strata in the vicinity of eruptive 

 rocks, that a reaction between silica and carbonate of lime takes place in the presence 

 of carbonate of soda, by which the alkali brought about, little by little, the solution of 

 the silica, and its union with the lime to form a hard silicate of lime. This is nature's 

 method. The action of alkali in dissolving the silica and then again giving it up to 

 the lime, was an example of many of the so-called actions by presence, which are really 

 cases of ordinary chemical affinity acting under peculiar conditions. It was reserved 

 for Mr. Eansome, by using both the lime and the silica in their free, soluble and active 

 forms, and by bringing in the alkali already combined with a portion of silica, to make 



