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Many of the coals comprised in the preceding table are defective by an absolute want of hydrogen; but several others, even those rich in hydrogen, by the association of that with a too strong proportion of oxygen, which in the distillation of coal disengages itself with the hydrogen, both being in a nascent state, are found in conditions favourable to combination; that is to say, to the production of water, to the detriment of the quantity of illuminating gas.

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We here perceive that the anthracites are absolutely wanting in hydrogen, independently of the consideration of oxygen. It explains then very well why this species of combustible is the least convenient. substance for the manufacture of illuminating gas.*

The results, according to the English engineer, Luke Herbert, obtained from a series of experiments made upon each of the three classes of English bituminous coals, and in each case by the distillation of one ton of the coal, are as follows:

1. Cannel coal of Lancaster produced 11,600 English cubic feet of

2. Coal of Newcastle, (Hartley mine,) 9,600 3. Coal of Staffordshire, best quality, 6,400

gas.

do.

do.

By experiments on a similar scale to the last, were obtained the following results:

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The gas obtained possessed an illuminating power much inferior to that from the coal of the first class; but there was much coke of good quality.

In this class the series terminates with the drier and less adhesive coals, called "open burning coals." open burning coals." Those of this kind are preferred by blacksmiths because they better bear the blast of the bellows.

ADAPTATION OF DIFFERENT VARIETIES OF COAL TO THE PURPOSES OF STEAM NAVIGATION.

There has been recently published a very elaborate report, of 607 pages, "to the Navy Department of the United States, on American

*Pelouze on Gas.

coals applicable to steam navigation and to other purposes, by Prof. Walter R. Johnson." It includes two hundred and one tables, prepared by the author with unusual care and under peculiar advantages, and furnishes the results of a long series of experimental investigations conducted at Washington.

Our space precludes our quoting extensively from this voluminous document: but we cannot refrain from selecting the following table

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of the relative degree of evaporative power of different coals under similar or uniform bulks. We select this table, at the suggestion of the author, in preference to that which exhibits "the order of evaporative power under equal weights." He remarks that coal, "when sold by weight and used on shore, the weight per cubic foot is a point of little moment. Space for stowage is easily obtained. But in steam navigation, bulk, as well as weight, demand attention; and a difference of twenty per cent., which experiment shows to exist between the highest and the lowest average weight of a cubic foot of different coals assumes a value of no little magnitude. This is obviously true, since, if other things be equal, the length of a voyage must depend on the amount of evaporative power afforded by the fuel which can be stowed in the bunkers of a steamer, always of limited capacity."

ADAPTATION OF COAL TO STEAM POWER.

We learn, through various channels, that the Lords of the Admiralty, in England, have taken up the subject of coal, not solely as relates to its economic working and consumption, but with reference to the probable quantities absolutely workable in Great Britain, the most economic methods of combustion, and the chemical properties and combinations of coal. An inquiry was announced as in progress, in the close of 1846, in reference to the value of coals for the use of the British steam navy. It is designed not merely to ascertain, by chemical analysis, the constituents of different sorts of coal, but, by an extensive series of comparative experiments, to determine their practical applicability. With this object in view, it is announced that steam boilers and furnaces have been erected at the Engineering College at Putney, and the examination is intrusted to Sir Henry de la Beche and Dr. Lyon Playfair, and those associated with them.

The editor of the Mining Journal remarks," "our beds of coal have been the undoubted production of ages; and, vast as they are, it appears the height of the ridiculous to assert, that they are inexhaustible. Every succeeding year brings its increasing consumption, not simply of tons, but of millions; and perhaps there is no other question in the range of political economy that deserves so much patient investigation, and no body of men so highly competent to the task as the gentlemen alluded to."

In order the better to follow up this interesting subject, illustrated in the last table, we proceed to append the results of a series of experiments to determine the evaporative values of several varieties of American coals-chiefly those of a semi-bituminous character. These investigations were undertaken by Messrs. Thompson, of New York, on account of the New York and Liverpool Steamship Company. As some of these results differ in certain respects from those of the last table, it has been judged expedient to precede them with the introductory notices of the experimenters.

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* Mining Journal, August 1st, 1846.

"E. K. COLLINS, Esq.

6

"Having received orders from you to test, by experiment, the evaporative values of several kinds of coal upon your Vertical Tubular Boiler,' and having discharged such duties, we hereby enclose you a copy of the report of said experiments with our views annexed.

"Our first experiment was with the Dauphin Rattling Run. It possesses high evaporative power, with considerable cohesion of its particles, so that it may not be broken into too small fragments by the constant attrition which it may experience in the vessel. It ignites very quick with natural draught, burns with a clear bright flame, leaving but a slight soot deposit upon the tubes, owing to the free circulation of the air through the grate bars, rendering the combustion more perfect. In short, it requires little if any attention from the fireman until it is necessary to charge the furnaces with a fresh supply of coal.

"Our second experiment was with the Baltimore Cumberland. It ignites rapidly, producing a strong heat; shortly after which time, it runs together, often adhering to the grate bars, requiring much time and labour to separate it. Without the strictest attention, in a short time, it would entirely exclude the air from penetrating through the interstices of the coal, thereby producing a great loss of steam. It has very small cohesion of its particles, requiring very careful handling to prevent it from crumbling into very small pieces.

"Our third and fourth experiments were with 'Young's Mining Company' and 'Maryland Mining Company.' They produce the same effect as the second experiment, the results being all forced.

"Our fifth experiment was with the Erie-possessing rapidity of ignition, makes an intense fire, throwing off an immense volume of carbonaceous matter, causing the tubes to fur up in a very short time, also having an undue quantity of sulphur in it.

"Our sixth experiment was with the Dauphin Rattling Run; varies nothing from the first experiment.

"Our seventh experiment was with the 'Maryland Mining Company;' results as before.

"Eighth experiment was with the Dauphin Backbone, slightly differing from the Rattling Run in evaporation and rapidity of igni

tion.

"Ninth experiment was with the Dauphin Rattling Run; still retaining the pre-eminence for marine purposes over any of the coals submitted for trial, requiring less labour by 75 per cent.-producing more steam in less time than any of the coals experimented with.

"Our tenth experiment was with the 'Maryland Mining Company.' Experienced the same difficulty as before, viz.:-running together, forming a heavy compact crust over the whole area of the grate, requiring frequent raking, that the air might circulate through and ignite the surface or top of the coals, thereby occasioning the furnace doors to remain open much longer than the circumstances of the case ought to justify.

"Having given a brief review of the coals submitted to us for trial, it may be well to add, that the Dauphin Rattling Run (for marine purposes) meets our decided approval, from the experiments we have had of it."

New York, Dec. 24th, 1850.

"Collins' Vertical

Table showing the economic values of the Coals consumed in a
Tubular Boiler," at the Novelty Works, New York, December, 1849.

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In 1852 was published the Report of the Engineer-in-Chief of the Navy, on the comparative value of anthracite and bituminous coal, from which we extract the following:

"The coals used for the experiments were the kinds furnished by. the agents of the government for the use of the United States Navy Yard and steamers, were taken indiscriminately from a pile in the yard without assorting. The bituminous coal was from the Cumberland Mines. The anthracite was the kind known as "White Ash Schuylkill."

From the experiments it appears, that in regard to "getting up steam," the anthracite exceeds the bituminous 36 per cent.

Again he remarks, "that from the experiments, without allowing for the difference of weight of coal that can be stowed in the same bulk, the engine using anthracite could steam about two-thirds longer than with the bituminous.

"These are important considerations in favour of anthracite coal for the uses of the navy; without taking into account the additional amount of anthracite more than bituminous that can be placed on

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