Varieties of Coal, with reference to their Adaptation to the making of Iron.

A, Coals which cannot be employed in iron works, in the crude state.

B, Coals which cement less in the fire, and which it is practicable to use raw in furnaces

worked with heated air.

C, Chiefly for illuminating gas.

CLASSIFICATION OF MINERAL COALS.

In the foregoing table of analysis of coals and anthracites we have so arranged them as to exhibit their varieties or gradations, and their distinguishing properties, in different countries. Hence, the European coals can readily be compared with those of America, and the adaptations of either may be assigned with some degree of confidence. We proceed to note these characteristic differences and agreements more in detail.

I. Fat Bituminous, blazing, coking.-In the first class, series A, of the table, by way of illustration, the English coals of the north, and some of the coals of Silesia, of Hesse, of France, and of Ame

rica, in the Ohio Valley, are chiefly fat and very adhesive or caking; swelling much in the fire. The hot air blast is successfully applied with these in the high furnaces. But, as their tendency to cement together in a solid mass, when in the fire, is such as to prevent a free draft or passage of the air through the furnace, it has been found indispensable to submit the coals to a preliminary process, and to reduce them to coke. Thus, the difficulty is wholly removed; and a light, cellular, and purely carbonaceous substance, easily ignited, is substituted for the unmanageable coal in its crude state. The average quantity of carbon which the English coals possess, is stated to be sixty-five per cent.

Series B, more southward, in Staffordshire and Derbyshire: these coals, although containing as much, and even more bitumen, do not melt together like those of Northumberland. They scarcely change their form even in the state of coke. The varieties, having this property, admit of their being used in the raw state, but require the introduction of hot air into the furnaces. Some of the American coals west of the Alleghany mountain have also these characters.

In regard to the manufacture of illuminating gas, the type of perfection, in the series C, is the Scotch cannel; then comes after it the Lancashire cannel, and, in the third order, the Yorkshire and Derbyshire cannel. With this class we would place the cannel coals of Kentucky, Indiana, Illinois and Missouri. This series can be assimilated, in many respects, to the coal of the basin of Mons in Belgium. The splint coal of Scotland is only a coarse variety of cannel, as are the greatest part of all the Scotch coals.

The Newcastle coals have a resemblance to those of Anzin, of Saint-Etienne, and of Rivè-de-Gier, the analysis of which we have placed in the series D.

II. Series E.-In the second class, the Scotch coals, although containing as much bitumen as those of the north of Scotland, are of the kind denominated dry coals. They cement together, but without change of form, and are not so adhesive as the fat English coals. These were heretofore coked before being put into the furnaces; but recent improvements have shown that, with the application of heated air, they can be employed without being previously carbonized. Their average proportion of carbon is about sixty per cent., and of bitumen 36 per cent. Some of the Alleghany coals will probably be found to assimilate with these. Approximating to the same class, to a certain point, will be found the coals of Auvergne and of a part of the south of France.

III. Series F.-We have assigned an intermediate space for a series of coals in the American coal basins which differ little from E except that they contain somewhat less of bitumen and more of car bon, viz. about 66 per cent. of carbon and 27 per cent. of bitumen and volatile matter, and are less adhesive and caking. The Heracles coal, in Anatolia, appears to belong to this series, and those of the Cantal and Puy de Dôme in France. These are convertible int

IV. Intermediate Series, very dry coals,-Semi-bituminous coals, -Steam coals.-In the fourth class, of which the Welsh coal of the southern and eastern districts is the type, and which possess only from twelve to twenty per cent. of volatile matter and bitumen, may be arranged those denominated "very dry coals, with excess of carbon." These do not cake or cement together in a mass, although each individual fragment is susceptible of conversion separately into coke, and consequently do not offer a similar obstruction to the current of air in the furnace, like those of the first class. It has, therefore, been found that they may be employed in a crude state in the cold air furnaces of South Wales. This class contains a larger proportion of carbon than the two others, being eighty-one per cent.

There exist both in France, Saxony and Belgium, coals which bear some resemblance to these. In the United States of America, particularly in Maryland, Virginia, and Pennsylvania, are some species which closely assimilate with the foregoing, usually denominated "open-burning," and sometimes "semi-bituminous," and are not surpassed by any known species for certain valuable properties.

Under this head may be arranged the culm of Kilkenny and of Glamorganshire, and the quality which prevails in some of the southern seams of the Welsh coal-field, and now universally known by the name of "steam coal," being supplied to the British marine steamers, and even to those of France and Egypt. The Welsh culm is a very light coal, of loose texture, very glossy, and composed of capillary fibres arranged in divergent rays. It burns easily, and without smoke, makes a lively fire, and is in great request in Swansea and Cornwall for the smelting of copper. Depots of steam coals are formed in the East and West Indies, and in various parts of the world, for the service of the English steamers.

There is in England another variety of coal, but not abundant, called flint coal, because it is almost as hard as flint, and has a shining fracture approaching to anthracite. The flew coal of the mines of Wedgebury in Staffordshire, belongs to this series. In Cumberland, at Alston Moor, a variety of coal is found, almost without bitumen, called crow coal, which approaches to the French coal of Fresnes.

V. In the fifth class are comprised the anthracites, or the nonbituminous coals. Our tables of analysis exhibit the component parts of this mineral from all the principal known deposits. In Pennsylvania it contains from 85 to 92 per cent. of carbon; in South Wales from 88 to 95; in France 80 to 83; in Saxony 81, and in Russia reaches 94 per cent.

After many years of unsuccessful trial in endeavouring to adapt this valuable mineral combustible to the manufacture of iron, the difficulties which at one time seemed insurmountable, were overcome both in Wales and in Pennsylvania, where many furnances, using the hot blast, are now in full activity. The domestic use of anthracite in the United States is very extensive, and annually increasing; all the original objections to its use having vanished.

In the United States of America the investigation of coal is of so

recent a date that we have scarcely had time to institute comparisons with the corresponding combustibles in Europe. Nor have we acquired more than a meagre amount of information in relation to the economic value of similar substances in other countries.

While in the new world, remarkable as it may appear, the most simple properties of mineral fuel have scarcely been known half a century; while the first anthracite found its way from Pottsville to Philadelphia in the year 1812; from the Lehigh region in 1814, and from Wilkesbarre in 1820;-while the first bituminous coal reached tide water down the Susquehanna only in 1804, the coals of England had been employed for fuel and manufactures from the beginning of the thirteenth century; those of Scotland towards the close of the same century; of France at the beginning of the fifteenth century, and in Belgium the coal mines had been in operation at least as early as the year 1198.

The amount of current information as to what has been effected, and as to what is the existing condition in other parts of the world in relation to coal mining industry and the enormous developments of this mineral in various countries, even during our own time, forms a department in industrial statistics which greatly needs elucidation, for the details which it embraces are by no means of easy access to the inquirer, either in the new or the old world. It is the growing necessity for such information, the demand for a multitude of essential data for which we have so often to seek in vain, that has led to the preparation of the present volume, and has encouraged its author to persevere. We feel assured, moreover, that in the concentration of such a multitude of useful facts which time has developed, but which are now, in great measure, for the first time brought together, we are conferring no slight accession to the generally prevailing knowledge, on a subject which is annually acquiring importance, and becoming more intimately connected with the advancement of the human race.

It may be useful to pursue these preliminary notes on the classifi cation of mineral combustibles somewhat further; and we, fortunately, are not without ample scientific authority for extending this section as far as our space will permit.

It has been perceived that similarity of results in analysis, is not of itself an entire and decisive guide to the ascertainment of all the properties of coal. Even as regards chemical results, apparently parallel, discrepancies are discoverable, when the investigation is carried further, which show the absence or presence of principles that materially influence operative results. Thus, in coals containing similar quantities of carbon, those of the north of England and in Scotland, for instance, the analytical results, acquired by Dr. Thomson, prove that the relative quantities of hydrogen, carbon, and azote, materially differ. Again, external properties and characters must likewise be consulted. The structure and texture of the coal, the density, the mode in which it burns in the fire, swells or decrepitates, and other phenomena must be attended to. We have seen, for example, that

some of the English coals possess so strong a tendency to melt, cement, and coke, as to form a hollow fire, and cannot be used in iron works without previous coking; while other coals, even such as possess ten or twenty per cent. more of bitumen, swell but little; and although their fragments cohere in the fire, they do not change their form and bulk, even in the process of coking.

There is yet another mode which has been employed to compare, with still greater delicacy, the respective qualities and composition of these combustibles. This is by means of the relative proportions of carbon and gaseous matters, ascertained more completely than is exhibited in the usual form of analysis. For a knowledge of these results, and some others that we propose to introduce, we are indebted in great measure, to the work of M. Pelouze on gas.

*

"All the compact coals, even the fattest, the most coking, the most inflammable-in a word, those which the English designate by the name of "close-burning coal," and which yield to distillation a coke, always more or less abundant, dense, and of better quality than those of the light coals-ought to be avoided for the manufacture of gas.

But among the eligible coals how many distinctions still remain to be made. We are often astonished to find that the lightest coal-that which leaves the least residuum after its combustion-above all, that which possesses characters entirely bituminous; which kindles rapidly and gives out a fine and elongated flame, yields much less gas to distillation than some other variety of the light coals which possess the same apparent characteristics, or which were even far from promising as much.

We are acquainted with a great number of analyses of coal, made at various periods; but all at a time when the science of the analysis of organic bodies had made little advances. Besides, the only object of those analyses was that of stating the respective proportions of coke, or de-bituminized coal, and the incombustible residuum which the coke yielded by a complete incineration. Little attention was given to determining the component parts of the bituminous portion. Mr. Richardson has devoted himself to researches in the laboratory of Professor Liebig, at Giesen. He has examined the English coals. We give the results of his analyses, the more willingly that his examinations have been directed to the produce in coke, and to the elements of the bituminous portion.

British Bituminous Coals.

With the certain means that chemists possess, now-a-days, for analysing organic substances, such a work, published by a person so competent in these matters ought to inspire confidence. Now we see that in the bituminous portion of the coals assayed by Mr. Richardson, the proportion of oxygen varies from 14.54 for 6.33 of hydrogen, to 5.50 for 5.31 of hydrogen. There is, therefore, reason to think,

* Traité de l'éclairage au Gaz, avec 24 planches, par Pelouze Pere, Paris, 1839.