18 tOALKIKLDS AND COLLIKKIKS OK AUSTRALIA. 



ammonia and pitch. The gas producing capabilities of the 

 mineral are stated to have amounted to 18,000 cubic feet per 

 ton, with an illuminating power of '_J8 to 40 candles, each 

 burning 120 grains of sperm per hour. 



Oil shales contain a preponderance of mineral matter. 



Lignite strictly speaking should show a woody structure. 

 13rown coal is a name given to a structureless variety which 

 generally contains a larger proportion of carbon and les 

 oxygen than true lignite. The color is generally brown or a 

 brownish-black, but is sometimes pitch-black. It kindles 

 readily and burns rather freely with a yellow flame and com- 

 paratively little smoke, but gives only a moderate heat. The 

 ash is often very light, so is readily blown about. It is always 

 high in moisture, which ranges between 10 and 20 per cent. 

 Uses of Coal. 



Good gas coal should have a IOAV percentage of ash, say 

 5 per cent. ; the sulphur should not be more than about 0.5 per 

 cent., while the volatile matter, which should be charged with 

 rich illuminating hydrocarbons, ought to be in the neigh- 

 borhood of 37 or 40 per cent. The coal should coke well, and 

 produce about 60 per cent, clean, strong, bright coke, after 

 carbonisation, which becomes a valuable product. 



For household purposes a coal should maintain a mild, 

 steady combustion, and remain ignited at a IOAV temperature 

 with a comparatively feeble draught. A. smoky flame is objec- 

 tionable as producing soot. A very free or fiercely-burning 

 coal is not desirable, as the temperature cannot be regulated. 

 If the coal contains pieces of slate they are apt to fly out into 

 the room. The ash must not be so stony that it cannot pass 

 through the bars of the grate, nor so light that it blows about 

 the room. Sulphur is objectionable ; it not only product's 

 stifling gases when the draught is bad, but it corrodes the 

 grate and tarnishes silver. 



Coal for use in a blacksmith's forge should possess a high 

 heating power. The amount of sulphur present should be 

 small, if any; the coal should also be low in ash. and it should 

 coke sufficiently to form an arch. 



Coal may be looked upon as consisting of gas, fixed carbon 

 and impurities water, sulphur and phosphorous. Coal, even 

 in the same seam, may vary considerably, as shown by 

 analysis, which have to be made occasionally, either for the in- 

 formation of the manager, or for selling contracts. The 

 nature of coal may be influenced by the kind of plants that 

 went to form it, also by the pressure to which it has been sub- 

 jected. Besides the ordinary proximate and ultimate analysis 

 of a coal, one should note other characteristics, such as if it is 

 tender and breaks up too readily, whether it is liable to spon- 

 taneous combustion, etc. 



