796 REPORT—1890. 
give blue stems, and the larger parts of plants, when numerous, give black, whilst 
mineral remains, owing to the quantity of oil they contain, give hardness and black- 
ness. The nodules are harder and contain most iron in the black shales. 
There is no great upheaval in the district, but the strata tell us their ever-- 
changing history as it went steadily on over a very long period of time. 
3. Some Physical Properties of the Coals of the Leeds District. 
By Bunsamin Horeare, F.G.8, 
The coals of this immediate neighbourhood have not been subjected to so many 
changes since their formation as have the coals of many other districts. 
Again, the variety of ways in which coals are used in the district give us. 
peculiar advantages in practically watching their behaviour under different condi- 
tions of combustion and distillation. 
The temperature at which coals are burnt has much to do with that behaviour. 
Thus, some coals which give a warm glow leaving a dry ash when burnt at the 
low temperature of a house fire might not be the best suited for use in the furnace 
of a boiler, and still less so for use in a reverberatory furnace for the manufacture 
and working of iron, steel, or glass, in which case coal is burnt at a very high tem- 
perature. These coal seams are those of the upper part of the lower and the 
lower part of the middle coal measures, and they are exceedingly variable in their 
physical properties and in their behaviour during combustion. 
There is the createst difference between coals of different horizons even of the 
same seam. Some have the cleat or cleavage wide apart, and contain very little 
mineral charcoal; they have a brown streak, and are very hard, being of a dull 
black colour. If thrown to the eround they give a sonorous ring. 
Immediately over or underlying these may be another coal with its cleat or 
cleavage very close, bright in appearance, easily broken, soft and light. 
It is evident that these two coals, lying in the same seam and having been 
subjected to the same geological conditions and changes, must have been originally 
made of very different materials. Between these two we have many varieties. 
If we slice the dull black coal in a vertical section we shall find that we cut through 
numerous resinous spores. If without slicing we grind and polish it vertically 
we find the same resinous spores protruding in the polished surface. Again, if we 
fracture the coal we can see with the naked eye the spores standing out on the: 
fractured surface; on the other hand the bright coals which break into smaller 
pieces cannot be sliced in sufliciently thin sections to be transparent. They 
contain more mineral charcoal, and from examination we may infer that they are 
made more of stems of plants than the others. This is still further proved by the 
examination of the baume pots which are found in the middle of coals of this kind. 
There are two coals, many feet apart, which have the same characteristics,. 
namely, the ‘better bed’ and one portion of the ‘ Middleton little coal.’ These are 
made up in a great measure of spores; their ash is not easily fused ; they contain 
a very small proportion of sulphide of iron or other fusible salts, so that they are 
best for use under circumstances where the temperature is high. 
The other coals, those with their cleat close together, when thrown upon the 
fire at once break down into small pieces which cool the fire, and by preventing 
the passage of a sufficient quantity of air are distilled more slowly and give off a 
different compound of gases from those given off by the coals with wider cleavage. 
This is the principal difference between a caking and a non-caking coal. They 
also contain a larger amount of sulphide of iron and different soluble and easily 
fusible salts, which go to make not only more ash, but ash of such a kind that 
it fuses and blocks up the spaces between the fire-bars, by this means pre— 
venting a more perfect combustion with our present rude methods of burning the 
coal. These fusible salts were not all present when the coals were originally 
placed where we find them, but they have been deposited by water since that time, 
and since the cleat was: formed, for they lie in the thin interstices of the cleat- 
It follows then that there is more ash and more sulphur in coals having a close 
cleavage than in those in which the cleavage is farther apart. This has come 
