60 REPORT 1870. 



On ihe Separation from Iron-Furnace Cinder of Phosplioric Add for Manuriul 

 Piirjjoses. By James Haegeeaves. 



On Artijidal Stone and variotis Jcinds of Silica. 

 By the Eev. H. Highton, M.A. 

 Silica is found in various forms, more or less insoluble. Some kinds can only 

 be united with alkalies in the heat of a glass-furnace ; other kinds can be dissolved 

 imder a high pressure, and after a considerable lapse of time, by solutions of al- 

 kalies ; other forms, again, to which the author particularly wished to call atten- 

 tion, can be dissolved under proper precautions even in the cold. Natural silica 

 of this kind was exhibited both from Germany and Enofland. 



By means of this soluble silica, artificial stone can be formed harder than any 

 natural stones, except the very hard granites and primitive rocks. The process is 

 as follows : — A concrete is made with any good hydraulic cement. When this 

 is dry, it is steeped in an alkaline solution of silica, in which is placed a quantity 

 of free silica. The following chemical process then takes place. The lime in the 

 concrete extracts the silica from the solution, leaving the alkali free, which im- 

 mediately attacks the free silica and conveys it in its turn to the concrete. This 

 process ^oes on continually till the lime in the concrete is saturated with silica. 



By this process, within a week the strength of the concrete is increased from 

 50 to 150 per cent. ; and by a longer continuation of the process the strength is 

 still more increased. 



The following is the comparative resistance to a crushing-force of several kinds 

 of stone : — 



lbs. 

 The silicated concrete, or patent Victoria stone, per square inch . . G441 



Aberdeen granite 7770 



Dartmoor granite 690.3 



Peterhead granite G210 



Yorkshire landing 6851 



Stafford blue brick 4032 



I'ortland stone 2426 



Bath stone 1244 



The stone formed in this manner has been tried as a pavement in the busiest 

 part of Cheapside, and in many other parts of London, and for steps, lintels, 

 sills, &c., in many parts both of this kingdom and abroad, as well as in India. 



The whole of the stone in the new warehouses, 27 St. Mary Axe, is made in 

 this manner. 



As a cheap strong stone, when manufactured on a large scale, it is likely to su- 

 persede natural stone, except where the latter is very cheap and abundant. 



In localities, as on the Thames, where there are facilities for obtaining good 

 hydraulic cement and hard broken stone, it can be manufactured at a much lower 

 cost than Yorkshire or other stone can be procured. 



On the Time needed for the completion of Ch^miccd Changes. ByDr. Hubtee. 



On the Prevention of Lead-poisoniny in Water. By A. Goedok. 



Various substitutes for lead piping have been tried, but all are more or less open 

 to objection. The substitute recommended by the author was that invented by 

 Mr. Haines, C.E. It consists of a leaden pipe with an internal pipe of block tin, 

 both having been previously pressed togetlier so as to form a homogeneous 

 whole. By this process the piping retained all the flexibility of lead, while 

 the inner tube of tin was strong and thick enough to prevent any access of water to 

 the exterior leaden pipe. 



On the Estimation of Sidphur in Coal-gas. By W. Mabeiott. 



