The coal was received generally in lumps, requiring to be reduced in order to be burned advantageously on the grate. Its aspect is that of most of the harder anthracites, possessing a deep black color, shining uneven and splintery fracture, with occasional exposure of conchoidal forms; a striated, rather grayish appearance, generally indicative of considerable portions of earthy impurity, marks certain surfaces. The seams of deposition are seldom followed by the frac tures.

The specific gravity of two specimens was found to be 1-6126 and 1.5679, from which the calculated weight per cubic foot are 100-79 and 97.99 pounds respectively, or on an average, 99.39 pounds.

The foregoing tables will, doubtless, give a satisfactory exhibit as to the relative value of the different coals named for steam navigation, iron making, or for generating steam ordinarily. For stove use, the following experiment will determine the respective value of the white and red-ash varieties. Two rooms of nearly the same size, and having the same temperature, were selected to ascertain how many pounds of each kind would be required to heat them to a temperature of 65 degrees, during a period of fifteen hours, when the temperature out of doors, at 9 A. M., was at ten degrees below the freezing point. Two days were occupied in the trial, so that the red and white-ash coals might be used in alternate rooms. Fires were made at 9 A. M. and continued until 12 P. M. Two thermometers (one in each room,) were suspended at the greatest distance from the grates, and the temperature was carefully registered every hour. The result was as follows thirty-one pounds, each day, of the Schuylkill red-ash coal, gave a mean temperature of 64 degrees; and thirty-seven pounds, each day, of the Lehigh white-ash, taken from a vein of high repute, gave a mean temperature of 63 degrees-thus making 2000 pounds of the red-ash to be equal to 2.387 pounds of the white-ash, or red-ash coal at $5.50 per ton, to be equal to white-ash ash at $4.61. This, says Mr. Taylor, settles the question between the two coals on the score of economy.

:

COMPARATIVE VALUE OF ANTHRACITE AND BITUMINOUS COALS. An impression has long prevailed that, for purposes of steam navigation, Cumberland coal was generally superior to anthracite, and it always enjoyed greater favor in the market. This impression must be destroyed-for a greater mistake never existed on the public mind. A series of experiments were recently instituted on several steamers of the United States Navy, under order of the government, the result of which is a triumphant vindication of anthracite coal, not only for steam vessels, but for generating steam under all circumstances-broadly establishing its vast superiority over bituminous and every other known coal. These experiments were brought about principally through the instrumentality of the Hon. James Cooper, our distinguished senator in Congress., The previous experiments of Prof. Johnson were unsatisfactory, because the tests were prosecuted on too small a scale to ascertain the real merits of anthracite ; and in the manner of burning it, he committed a mistake which led him greatly to depreciate its value compared with Cumberland coal, in equal weight. These mistakes were apparent to Mr. Cooper, and he therefore took up the subject, and called the attention of Congress to it. A resolution offered by him was passed at once, requiring the Secretary of the Navy to institute experiments, the result of which we shall lay before the reader. Mr. Cooper resides at Pottsville, and his exertions in asserting, and thus establishing, with the broad seal of the United States government, the superiority of anthracite over all other coals, are deserving, and will receive, the lasting thanks of the thousands engaged in the trade of Pennsylvania.

Experiments with Bituminous Coal, made with the boilers of the United States Steamer Fulton, at the New York Navy Yard, January, 1852.

The temperature of the water in the boilers being at 38° F., and the temperature of the boiler room 18°, the fires were lighted at ten hours thirty minutes, A. M. At eleven hours forty minutes, A. M., the temperature of the water was 212° F., and steam began to be generated at the atmospheric pressure. Time raising steam, seventy minutes. The temperature of the boiler-room had now increased from 18° to 32° F. At eleven hours fifty-four minutes, A. M. the steam pressure in the boilers was thirty pounds per square inch above the atmosphere. Time of obtaining thirty pounds of steam, one hour twenty-four minutes from a temperature of 32° F. Up to this time there had been fed into the furnaces one

thousand pounds of dry pine wood, equal to five hundred pounds of coal, and two thousand eight hundred and twenty-six pounds of (Cumberland) bituminous coal. Total, three thousand three hundred and twenty-six pounds.

The engine was now set in operation to work off all the steam, which the above amount of coal would generate, no more being fed to the furnaces. In fiftythree minutes the steam pressure was reduced from forty pounds to five pounds, and the number of double strokes of piston made from forty-one to seven, when the engine was stopped. During the time the engine was in operation, the steam was cut off at half-stroke.

The engine consisted of one cylinder, fifty inches in diameter, and ten feet four inches stroke. The space between the cut-off valve and piston, including clearance, to be filled with steam per stroke is 3.094 cubic feet. The calculation of the amount of water evaporated is made from the quantities of steam measured out by the cylinder, divided by the relative bulks of steam of the experimental pressures and the water from which it is generated.

The initial pressure of the steam in the cylinder is taken at one pound less than in the boilers. The space displacement of piston filled with steam, per stroke, is 70-448 cubic feet, to which must be added the above 3.094 cubic feet, making a total of 73.542 cubic feet.

Time.-Minutes.

Pressure above atmos-[Number of double strokes Cubic feet of water
phere, per square
of piston made.

evaporated.

inch, in pounds.

Taking the weight of a cubic foot of sea water at 64.3 pounds, the total weight evaporated is (51-911 64-3)=3337-877 pounds. The boilers of the Fulton contained 82.000 pounds of water at the initial temperature of 32° F., which was raised to 212° F., and 3337-877 pounds of it evaporated by three thousand three hundred and twenty-six pounds of coal.

Now it requires five times and a half as much caloric to evaporate a given bulk of water from a temperature 212° F., so as to raise it to that temperature from 32° F. The quantity of fuel, therefore, expended in raising the water from the initial temperature to that of 212° F., compared to that expended in evaporating the 3337.877 pounds from that temperature, will be as (82·000 × 180°)=14,760,000 to (3337-877 × 990°)=3,304,498.23, or as 4.4666 to 1.000; consequently

3326 4.4666

-744-6 pounds of coal were consumed in evaporating 3337.87 pounds of sea-water, or 4-483 pounds of water per pound of coal. It was intended to have made, on the following day, an experiment, under precisely the same circumstances as above, with anthracite; but it was found impossible from the presence of ice to work the engine, the experiment was therefore only made so far as regards the time of getting up steam, with the following results, viz:

The fires were lighted with the same quantity and kind of wood, and the same quantity of coal that had been used the day previous. At seven hours and twenty minutes, A. M. the temperature of the water in the boiler being 38° F., and that of the boiler room 32° F., with the natural draft, the temperature of the water at eight hours and five minutes was 212° (steam,) and the boiler room 43, F. Time to generate steam, forty-five minutes. At eight hours and twenty minutes the steam pressure in the boiler was thirty pounds per square inch. Time of obtaining thirty pounds of steam from water at 88° F. was one hour.

With the bituminous coal it will be seen that it required seventy minutes to obtain steam from water at the temperature of 32° F., while it only required forty-five minutes with the anthracite; being a difference of time in this respect of about thirty-six per cent. of the bituminous time.

The data for a comparison of the evaporative values of the coals was obtained by another experiment as follows:

Experiments with White Ash Anthracite made with the boilers of the United States Steamer Fulton, in New York Bay, January 1, 1852.

This experiment was made with the steamer under way, while steaming with steady pressure of steam and revolutions of the wheel, as follows:

Steam pressure (initial) in cylinder per square inch above the atmosphere, twenty-five pounds; double strokes of piston per minute, twenty-one and onethird; cutting off at from commencement of stroke, three-eighths; consumption of coal per hour, eighteen hundred pounds.

From the above data, there was filled per stroke 52.837 cubic feet of the space displacement of the piston, to which add 3·096 cubic feet of space comprised between the cut-off valve and piston, making a total of 55.931 cubic feet of steam of twenty-five pounds pressure, which would be per minute 55-931 X42%=2386·39 cubic feet, and per hour 143,183.40 cubic feet. Dividing this last number by the relative bulks of steam of the pressure generated, and the water from which it was generated, we obtain 143183.40 -209-332 cubic feet of sea-water, which at 64.3 pounds per cubic foot, amounts to 13,460-047 pounds, evaporated by eighteen hundred pounds of coal, or seven thousand four hundred and seventypounds of sea-water per pound of coal.

684

3. Experiment with White Ash Anthracite Coal made with the boilers of the pumping-engine at the United States Dry Dock, New York Navy Yard.

A comparative experiment was made with the boilers of the pumping-engine at the New York Navy Yard, in October, 1851, on the comparative advantages

of anthracite and bituminous coals; all the conditions were as nearly alike as practicable. With the anthracite coal a combustion of nine hundred and eighty pounds per hour, evaporated a sufficient quantity of water to supply the engine with steam of twelve pounds pressure above the atmosphere, per square inch, for four hundred and twenty-five double strokes of piston per hour, the steam pressures being alike in both cases; the economical values of the coals will be represented by the number of double strokes of piston made, divided by the quantity of fuel per given unit of time; or will be, anthracite =0.4337: bituminous 0.2673, or the anthracite is better than the bituminous in the proportion 1.623 to 1.000.

1100

of

0-433T 0.2637

425 980

It is proper to remark that these boilers were expressly designed for burning bituminous coal.

The coals used in these experiments were the kinds furnished by the agents of the government for the use of the United States Navy Yard and Steamers, and was taken indiscriminately from the piles in the yard without assorting.

The bituminous was from the "Cumberland" mines. The anthracite was the kind known as 66 White Ash Schuylkill."

From the preceding data, it appears that in regard to the rapidity of "getting up" steam, the anthracite exceeds the bituminous thirty-six per cent.

That in economical evaporation per unit of fuel, the anthracite exceeds the bituminous in the proportion of 7-478 to 4-483 or 66.8 per cent.

It will also be perceived, that the result of the third experiment on the boilers of the pumping-engine at the New York Dry Dock, which experiment was entirely differently made and calculated from the first and second experiments. gave an economical superiority to the anthracite over the bituminous of 62 per cent.; a remarkably close approximation to the result obtained by the experiments on the "Fulton's" boilers, (66-8 per cent.,) particularly when it is stated that the boilers and grates of the pumping-engine were made with a view to burning bituminous coal, which has been used since their completion; while those of the "Fulton" were constructed for the use of anthracite. The general characters of the boilers were similar, both having return drop flues.

Thus it will be seen, from the experiments, that, 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 bituminous.

These are important considerations in favor 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 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.