134 



Barmm. 



plumlDago. 



Case iC6. 



Cement. 



The Victorian tripolite is of exceptionally fine quality, both as 

 regards colour and texture. The German earths have an 

 admixture of carbonaceous matter which, when once ignited, 

 emits enough heat for drying purposes. For New South Wales 

 earths, and remarks on tripolite, see page 96. 



Salts of barium are used in the arts, and the sulphate, harytes^ 

 is employed with white lead in the manufacture of paint. 

 Witlierite, the carbonate of baryta, occurs in the north of 

 England ; it has not been found in New South Wales. Barytes 

 is of common occurrence in mineral veins. It is of commercial 

 value only when of great purity, and perfectly white in colour. 



Black Lead, Grapliite — Carbon' with more or less impurity. 

 Used for crucibles, pencils, lubricating, stove polishing, foundry 

 and other purposes. 



Ceylon, Eussia, Mexico, Bohemia, Queensland. 



Ceylon is the principal source of graphite of high quality. 

 The purest material (96 per cent, carbon) is used for crucibles, 

 while the very finest, after sifting through silk sieves, is 

 employed in stereotyping and for lubricating. Graphite con- 

 taining 70 per cent, carbon is used for foundry and general 

 purposes. The Mexican graphite (87 per cent, carbon) is used 

 for stove polish and for pencils. The Bohemian (60 per cent. 

 carbon), for foundry work and stove polish. 



Fortland Cement^ without entering into details, is a material 

 resulting from the calcination, carried to the point of incipient 

 fusion, of an intimate admixture of calcareous and argillaceous 

 substances. After calcination the material is ground to the fine- 

 ness of flour — 90 per cent, passing through a 5,800-mesh sieve. 

 Some of the crude materials used in the manufacture of Portland 

 Cement in Great Britain are exhibited. By an admixture of 

 chalk (carbonate of lime) with the various clays and muds used, 

 any desired combination can be arrived at. 



Analyses of some of the raw materials and of the cements will 

 be found in the case. 



