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Transactions of the Society. 
coal resources of the country are in private hands the collieries 
themselves should contribute to the expense incurred. 
The demand for coal has generally been equal to, or in excess 
of, the quantity raised, otherwise one would have expected the 
more enterprising colliery companies to have had made a detailed 
examination of their seams. One or two such surveys have been 
attempted but never completed. Such an examination would 
enable the collieries to state the types of coal they could supply. 
Much valuable hard coal is wasted through being mixed with 
softer varieties, considerable inconvenience being experienced. 
Black smoke from boilers can often be traced to the presence of 
hard cannel coal in the fuel used. Much of our present smoke 
trouble could be minimised if more attention were given to the 
securing of unmixed supplies of fuel. The micro-examination of a 
mixed seam, from floor to roof, would tell whether there was 
a sufficiency of one type of coal to justify separate working. 
Though the use of mixed types of coal is to be deprecated 
when the mixtures are an unknown quantity, a good hard coal can 
be made to carry a proportion of a softer coal without detriment to 
its characteristic properties, if carefully and judiciously mixed. 
Some coking coals will also carry a proportion of a coal of inferior 
coking properties, or if a good spore coal is used in recovery gas 
practice a proportion of humic coal can be carried. The high 
nitrogen content of the latter will increase the ammonia yield. 
If the collieries were able to state their types of coal, a purchaser 
could choose the type most suitable for his needs, or have definite 
mixtures made. He would require very little other information. 
