I have been furnished with a copy of their journal, from which I take the following:

"Passage down, 'common thrust;' revolutions, 5,070; time, 83 minutes.

"Passage down, patent thrust;' revolutions, 5,012; time, 77 minutes.

"Passage up, 6

minutes.

ccommon thrust;' revolutions, 8,090; time, 128 "Passage up, 'patent thrust;' revolutions, 7,500; time, 114 minutes."

Had there been, during the passage down, an equal advantage in loads, tide, and distance, the slower speed should have made the least number of revolutions in proportion to the distance, the tide would have carried them in the difference between the times as the same revolutions of screw should have carried them an equal distance through the water under similar circumstances. The distance propelled for each revolution of the screw is not in any way affected by the "thrust bearing."

The results can be approximated by taking the revolutions, pressure, time, and coal in one case, and the revolutions and pressure in the other, and from thence find what should be the coal and time in the former case under similar circumstances of load, &c.

"Common thrust."-Total revolution, 13,194; revolution per minute, 62.66; time, 210 minutes; coal, 1,182 lbs.

"Patent thrust."-Total revolution, 12,512; revolution per minute, 65.55; time, 191 minutes; coal, 765 lbs.

Taking the data for patent thrust as the basis of calculation, we obtain as follows: x 765 807, and as the relative volume corresponding to 60 pounds pressure is to the volume of 60 5 pounds, so is 807 to 802; then reducing this to the same number of revolu tions in each case, it becomes 13514 × 802760, or five pounds less coal than with the patent thrust for the difference of pressures, but the times are as 191 to 199 in favor of the patent thrust.

The average revolutions per minute stands as 62.66 to 65.55, also in favor of the patent, but when these are equalized to the revolutions due to the pressures they stand as 63.20 to 65.55, the respective squares of these results indicating the relative gain, the former 8 and the latter 7 per cent. But if the load, tide, distance or other conditions apart from the thrust varied in the two trials, this result would be vitiated in the same ratio. The ordinary thrust used upon this occasion was an imperfect affair as would appear from the following extract from their report: "The ordinary thrust bearing used was quite rough from overheating, consequent upon which more power was absorbed in friction than otherwise would have been."

I am not aware of any satisfactory data from which correct conclusions can be deduced as to the real value of this invention.

I am, respectfully, your obedient servant,

Hon. J. C. DOBBIN,

Secretary of the Navy.

DANIEL B. MARTIN,

Engineer in Chief, U. S. N.

The next report was made February 6, 1857, by Chief Engineer King; this report does not give any material facts in relation to economy of fuel but it being important to show the merits of the invention, we insert it:

UNITED STATES STEAM FRIGATE "WABASH,"

Brooklyn, New York, February 6, 1857. SIR: In compliance with your order, directing me to report the results of any trials or experiments made here with "Parry's antifriction box," in comparison with the ordinary "thrust bearing," I have to state that no experiments have been made on board this vessel for the purpose of testing the relative value of the two kinds of instruments as regards economy of fuel.

It was my intention, from the first application of the patent thrust to this ship to make careful and accurate experiments of comparison; but we have been obliged to depend entirely upon the patent thrust, and have not as yet deemed it prudent to use the ordinary one sufficiently long to conduct the experiments.

During our voyage to Aspinwall, I removed the whole power from the patent to the ordinary thrust, with the intention of using it several hours, and noting the results necessary for calculation; but it soon began to heat, and as we already had much difficulty in keeping other bearings sufficiently cool to work them, I reluctantly abandoned the attempt to use it hence to secure necessary data.

It may not be out of place here to say that the "patent anti-friction box" has given more than ordinary satisfaction to the engineers of this ship. It is durable, correct, and beautiful in its operation, requiring no attention, except a few drops of oil occasionally. Up to this time, it shows no evidence whatever of wear, nor is there the slightest probability of its getting out of order within the next ten years. I consider the invention a highly important and valuable appendage to screw steamers.

Respectfully, your obedient servant,

Commodore PAULDING,

J. W. KING, Chief Engineer United States navy.

Commanding United States Home Squadron.

The next report, found on the files of the "department," was made May 19, 1857, by Chief Engineers Williamson, Follansbee, and Archbold, based upon trials made on board of the United States steam frigate "Minnesota."

UNITED STATES NAVY YARD,
Philadelphia, May 19, 1857.

SIR: In obedience to your order of the 9th instant, we have tested the relative advantages of the two plans for receiving the thrust of the propeller on board the "Minnesota," and respectfully report that in order to arrive at reliable results the engines, &c, were operated, on the 15th instant, with the "collar thrust," and again on 16th instant with "Parry's thrust;" the same amount of fuel expended on both occasions, the times of tides, pressures of steam, revolutions of engines, expansion, and all other conditions that would affect the results, were carefully observed, reudering the trials (as nearly as possible) similar; the experiments were continued, on both trials, until the steam had fallen to five pounds per square inch.

The result of the experiments is shown by the enclosed logs, from which we find the number of revolutions with "Parry's thrust" to exceed those made with the "collar thrust" by 387 revolutions, or 5.43 per cent., which we take to be the saving in fuel; the oil used on the "collar thrust" was eight times the quantity used on "Parry's." The hot journals, different states of atmosphere, and reduced average of vacuum on the first day's trial, was somewhat in favor of "Parry's thrust."

In estimating the value of "Parry's thrust" for each vessel, it is, in our opinion, necessary to consider, carefully, the saving of fuel and oil, and the security from heating the thrust bearing, which is far removed from the eye of the engineer of the watch; also in limitation of its value, to consider the proportion of time which the machine will be used, the absolute necessity of using it at all, and the probability of its being superseded by other contrivances.

After a careful consideration of all these elements, we are of opinion that a fair valuation would be two thousand dollars ($2,000) for its use in each vessel of similar size and power to the "Minnesota."

We are, respectfully, &c., your obedient servants,
WM. P. WILLIAMSON.
JOSHUA FOLLANSBEE,
SAMUEL ARCHBOLD,
Chief Engineers, U. S. N.

Commodore CHARLES STEWART,
Commandant Navy Yard, Philadelphia.

Remarks.

Steam log kept at the time of testing the collared thrust on board the "Minnesota," navy yard Philadelphia, May 15, 1857.

Steam log kept at the time of testing Parry's thrust, on board the Minnesota, navy yard, Philadelphia, May 16, 1857.

REMARKS.-Started fires at 10h. a. m.; used 90 feet of kindling wood; atmosphere in a good state for combustion. Temperature of water in boilers, before firing up, 63° Fahr.; when steam was raised, water and steam in top gauge-cocks; started engines at 53m. p. m. Thrust, by dynamometer, at 30 revolutions, 21, 300 pounds. Engines working well and journals cool; at 1h. 30m. p. m., a little water on crank pins; all other journals and bearings cool and oiled. At 4h. 7m. p. m., stopped engines 13m. to correspond with stoppage of the 15th instant; at 4h. 20m., started engines; at 5h. 20m., stopped engines, steam having fallen to 5 pounds. Coal consumed in the trial, 137 buckets, weighing 115 pounds each, 15,812. 5 pounds. Oil used on Parry's thrust, 14 gills. Register started at 31525; at 5h. 20m. p. m., stood at 39039. Revolutions made during trial, 7,514.

The next was made by the engineer-in-chief, May 21, 1857; this report is based upon the data given in the last.

OFFICE OF ENGINEER-IN-CHIEF,

Washington, D. C., May 21, 1857. SIR: In obedience to your order I have examined the trials made on the United States steam frigate "Minnesota," of the "Parry," and common thrust, and from the logs kept have deducted the following table:

From the remarks of the different day's trials, it will be observed that on the day the common thrust was tried the weather was rainy and the atmosphere in a bad state for combustion; the day the "Parry" thrust was tried, the "atmosphere was in a good state for