135 



Cements may be either slow- or quick-sotting ; a slow cement 

 taking two hours or more. By long storage it becomes slower 

 in setting and increases in tensile strength. They are generally 

 used with more or less sand. The tensile strength is determined 

 by the breaking of test briquettes, some o£ which are exhibited. 



Exhibits from the CuUen Bullen Companies, of 'New South 

 Wales, in addition to those from Ibreign localities, are placed 

 here. 



Soman Cement is one of the quick-setting class, becoming 

 hydrated in a few minutes. It is prepared from the calcareous 

 clay nodules so abundant in the London Clay Formation of the 

 S.E. of England. It is not nearly equal in strength to the 

 Portland. The septaria are crushed, strongly calcined, and 

 jjowdered. Septaria from different localities are frequently 

 mixed. Magnesia is quite harmless in these quick-setting 

 cements. 



Plaster of Paris, Parian Cement, Sf'c. 



Patent Fuel, England. The patent fuel is prepared from very CaSG 107. 

 small, cleaned coal. The latter is crushed and mixed with 9 to patent FneL 

 10 per cent, of pitch prepared from coal tar.* After subjecting 

 to hot air or steam to soften the pitch, the material is moulded 

 into briquettes by hydraulic pressure. The whole operation is 

 automatic. 



The briquettes are harder, and require much less space for 

 packing, than coal. 



Coke from England and the United States. Coke. 



Large deposits occur in some of the Midland counties of Qass 

 England. The salt is generally converted into brine and pumped jjoc]^ g^it. 

 to the surface. Brine and prepared salt in different stages for 

 various purposes, is exhibited. 



Borax, borate of sodium, California. Borates. 



Priceite, borate of lime, Oregon. 



* After extraetins the pitch, carbolic acid, &c., can be obtained from the residue of the 

 coal tar. 



