408 Analym of Scientific Boohi. 



" To convert Common Lime into Hydraulic Lime* — The ope- 

 ration to be described is a true synthesis, which, by the action 

 of fire, unites, in an intimate manner, the essential principles 

 which analysis separates from hydraulic lime. The lime to be 

 modified is to be left in a dry and covered place, until reduced 

 spontaneously into powder, and afterwards mixed, by the aid of 

 a little water, with a certain quantity of grey or brown clay, or 

 simply with brick- earth, and this made into balls, which when 

 dry, are to be heated to the necessary degr-ec. 



** Common lime will require 20 per cent, of clay ; intermediate 

 limestone will require 15 per cent. ; and 10, or even 6, will be 

 sufficient for those which already possess hydraulic properties 

 to a certain extent. When the quantity is raised to 33 or 40, 

 the lime obtained will not slack, but is easily pulverized, and 

 will make a paste that hardens very readily under water. When 

 the clay is mixed with pebbles, ^c, it is to be thrown into a 

 large quantity of water, well mixed with it, t^nd the finer part 

 run off into a convenient place* It may then be mixed with the 

 lime in powder, and made into balls ; the quantity required is 

 easily ascertained by a little practice. 



" It must not be supposed that the clay baked alone, and 

 then added to common lime, in the proportions mentioned, will 

 give the same results as when the two substances are mixed 

 before being heated. The fire modifies the one substance by 

 the other, and gives rise to a new compound, which enjoys new 

 properties." — p. 7. 



" If fragments of common lime, and a mixture of coal and char-* 

 coal be placed, stratum super stratum, in a small brick furnace, 

 and burnt ; and if, as the substances fall by the dissipation of the 

 combustible, the lime, which passes through with the cinders, 

 be returned with fresh fuel to the furnace, and the process be 

 continued 15 or 20 hours, according to the size of the frag- 

 ments, an over-calcined lime will be obtained, which will not 

 slake, but which, when reduced into a fine powder, and made 

 into a ductile paste, has the property of hardening under water." 

 —p. 15. 



