board a vessel in the same bunkers, or the advantages of being free from smoke, which in a war steamer may at times be of the utmost importance in concealing the movements of the vessel, and also the almost, if not altogether, entire freedom from spontaneous combustion.' "The following tabular statement shows the actual evaporation of water effected by bituminous and anthracite coals in the boilers of several naval steamers, and in those of some trans-atlantic and river steamers plying to and from New York the past few years:-" "From the averages of the above table it will be seen that the economical evaporation by the anthracite exceeded that by the bituminous in the proportion of 7.235 to 5.142, or about forty-one per centum of the latter." "In the experiments made on coals by Playfair and De la Beche, by order of the British government, in 1848, were found eleven varieties of Welch coals having a constitution almost identical with the nine specimens of Pennsylvania anthracite, experimented on by Prof. W. R. Johnson, viz:” *Pittsburg coal. † Cumberland coal. ‡ Virginia coal. ? Scotch coal. "The average evaporation of water by the Welch anthracite and by the Pennsylvania anthracite was as follows: Fresh water evaporated from the temperature of 212 deg. F., by one pound of coal. By Welch anthracite, By Pennsylvania anthracite,. pounds . . 9.263 9.590 "Thus far there is a very close agreement between the results obtained by the different experimenters from substantially the same coal-that coal being anthracite. "In the experiments of Playfair and De la Beche, above cited, we find three varieties of Welch bituminous, three varieties of Scotch bituminous, and one variety of English bituminous, having a constitution almost identical with the five specimens of Maryland (Cumberland) bituminous coal experimented on by Prof. W. R. Johnson." "The average evaporation by the Welch, Scotch and English bituminous and by the Cumberland bituminous was as follows, viz: Fresh water evaporated from a temperature of 212 deg. F., by one pound of coal By Welch, Scotch and English bituminous. pounds. 8.02 9.93 "Here is a great discrepancy between the results obtained by the two experimenters on substantially the same coals; Prof. W. R. Johnson making the Cumberland bituminous better than the British bituminous. in the proportion of no less than 24 per centum of the latter. Had a similar difference been found in the case of anthracite between the re sults of the two experiments it might have been accounted for by a difference of boiler or method of conducting the experiments. We are sorry our limits will not allow of further extracts from the reports. Dr. Higgins, in his Report for 1854, p. 72, expresses himself strongly in favour of the superiority of the Cumberland coal, especially for steam navigation, for which he deems three qualities essential in a coal, “quickness of combustion, continuance of combustion, and steady combustion. Fuel should take fire rapidly, it should burn for a long time, and its intensity should not be diminished by fresh additions of material." Excepting the first, anthracite has these qualities, and a steam-ship is not a factory where the fires are extinguished every night-and even if they were, proper coal and other free-burning fuel could be supplied for kindling, and such emergencies as may arise. In the region supplied by the Susquehanna coals, the hard anthracites are extensively used for stationary steam-boilers, where the various grades from Karthaus bituminous and Dauphin semi-bituminous, to the Lyken's valley or Bear-gap free-burning anthracite, are accessible-in some cases where a fire has to be renewed every morning, and in others where it is kept up without intermission for several months. Dr. Higgins says "The policy of the world at present is for steam navigation, not only for commercial, but also for warlike purposes. A steam vessel of war requires, above all others, to have a fuel which can speedily generate and keep up a steady head of steam, whether in pursuit of, fleeing from, or in actual combat with an enemy. A minute's delay may prove disastrous; the increased revolution of the paddle-wheels for a few times will frequently insure success. Our national flag may float gloriously over the sea, or be stricken from the mast, as the ship which bears it is well or ill supplied with fuel, and these ships should always use the Cumberland coal. Our navy should learn from the experience of our commercial marine, and this teaches it that the best coal for steam navigation is the Cumberland coal." The following tables are then given of the time required to cross the Atlantic by the Collins and Cunard In favour of Collins for the year (27 voyages), 22 12 35 "From this there was the novel fact of the Cunard line, steamers of British build, being swifter on the Eastern passage than the Collins line, steamers of American build. On their Western passage quite the reverse took place. . . "Many explained the difference between these vessels as to their respective superiority on their eastern and western passage, by their different powers in going with or against the wind. The result, however, was to be explained by their different means of propulsion as to the generation of steam. I therefore addressed a letter to the proprietors of each of these lines, and received the following replies: "New York, January 19th, 1854. "DEAR SIR,-Messrs. Brown, Bro. & Co. have handed me yours of the 17th inst., making inquiries relative to the coal used by us. Our first trial was with the Cumberland; but finding so much slate and earthy matter in it, we were compelled to try the Anthracite, which we have been using for the past three years; but from what I learn of the Cumberland mines, I think we will soon give that coal another trial. From Liverpool we use the Welch. The Cunard Co. use the Cumberland, not being able to burn the anthracite in their furnaces. Yours respectfully, "E. K. COLLINS.' "New York, January 19th, 1854. "SIR:-In reply to the inquiry made in your letter of the 17th instant, I beg to inform you that on the voyage from England to America, we use Welch coal for fuel on board our steam-ships, and Cumberland coal on the voyage from America to England. "I remain, &c. "E. CUNARD.' "The reason of the difference was now satisfactorily explained. It was in the superiority of the Cumberland over the anthracite coal. When these steamers used the same coal (the Welch), American shipbuilding proved its superiority, for the American ships (the Collins. Line) proved themselves the faster; but even superior American naval architecture could not compete with English ships, when those ships used Maryland coal, for then they surpassed in speed the American ships using the anthracite coal." Prof. H. D. Rogers, State Geologist for Pennsylvania, has permitted us to give his authority as to the value of anthracite for steam navigation. He states that it is less adapted for steam navigation, in proportion to the quantity of volatile matter. Mr. S. V. Merrick, of Philadelphia, who enjoys the highest repu tation in all that relates to the manufacture and employment of steam machinery, assigns the first place to anthracite, the second to Welch, and the third to Cumberland coal. In a recent letter (March 2d), he expresses doubts about the accuracy of Dr. Higgins, in attributing the more rapid outward passage of the Cunard ships to the coal used, and were this the case, "it would prove nothing, as these boilers are adapted specially to the bituminous, and will not work economically with the anthracite." The results of the laboratory experiments of Professor W. R. Johnson, must be adopted with great caution in deciding upon cases where the circumstances are different, and the quality of the coal possibly different from the samples used by him. Such experiments afford valuable collateral aid as indications of the direction which practice should take for their verification, but their evidence is far from being sufficient to settle the question. This must be accomplished by steady and varied practice, under different circumstances. We conclude these various experiments and remarks on the adaptation of coal to steam power, by appending the following account of the semi-bituminous coals of the Welch Basin, from the foreign portion of the first edition of this work,* p. 362. Semi-bituminous Coals of the Welch Basin.-Steam coals or intermediate of the southern side of the basin. Towards the close of 1840, an association was formed in London for the encouragement and protection of the Welch coal trade. They remark that "the durability of the ordinary bituminous coal, the very peculiar qualities of the anthracite or stone coal, and the great superiority of the intermediate or steam-packet coal of South Wales, are now so well ascertained, that it would appear as if nothing more were required to insure a preference at all the places of import which can be reached at a moderate rate of freight. It has only been, however, by very small degrees, by very great individual exertions, and by very considerable private loss, that the Welch coal has just begun to obtain a reputation in the port of London."† The semi-bituminous coal of the south part of this basin, possesses many characters in common with certain coals in Pennsylvania; both of them being admirably adapted for steam engines; so much so as to have received the specific title of "steam coal.”‡ The Craigola coal has been recommended for similar qualities; and the Llangennech has established for itself a higher reputation as a steam coal, and has been used on board steam ships in various parts * Since the above publication, we understand a new geological survey of England and Wales is progressing-the maps are on a scale of 1 inch to a mile and of great accuracy and excellence. "The principal coal strata are traced nearly throughout the complex involutions of the surface with surprising accuracy and effect; and even the Faults are laid down with distinctness,-ranging with an approach to parallelism, from about S. E. to N. W., but in some places singularly complicated; and their connection with the features of the surface is clearly shown. The horizontal sections with the vertical leave nothing to be desired, and the whole work forms a subject of most instructive study to geologists."-Edinburgh Review, October, 1849; Review of Statistics of Coal. † Mining Journal, Vol. X. p. 359, 1840; and Cambrian Newspaper. Monmouthshire Merlin, 1840. |