Mr. Churchill made some remarks upon the use of steam in desulphurizing

ores.

'On motion of Mr. Dibben it was voted that the meetings of the society, during the summer, should be held monthly, on the second Thursday of each month, and the society adjourned to the second Thursday in July.

JOHN K. FISHER, Secretary pro tem.

AMERICAN INSTITUTE POLYTECHNIC ASSOCIATION,

July 10, 1862.

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Prof. CHARLES A. SEELY in the chair.

THOMPSON'S AUTOMATIC GAS REGULATOR.

Mr. Churchill, from the committee appointed to examine this invention, made the following report:

To the Polytechnic Association of the American Institute:

Your committee, appointed to examine Thompson's automatic gas regulator, submit the following report:

Table I, hereto appended, presents the mean of several readings on the meter at the pressures under which observation were taken.

The double lines, intersected between the base line and the line of each burner, being proportionable to the consumption.

Table I, column 1st, shows the pressures. Column 2d shows the ratio of consumption (100-6 cubic feet per burner). Column 3d shows the ratio of light by the photometer. Column 4th shows the ratio of light if the gas had been burnt at all of these pressures with the maximum of economy obtained at 1.5 inch pressure. Column 5th shows the ratio of the difference between columns three and four, supposing the unit of light equal to sixteen candles.

Some delay was occasioned in preparing the trials, in order that compliance might be obtained with the point insisted on by your committee, viz: that the articles sent to be tested should be such as were furnished for sale.

These experiments show that the improved burner No. 1 was adapted to burn with a maximum variation of 1000 of 1 cubic foot per minute, with pressure varying form 1.5 inch to 3 inches, and the burner No. 2 was able to produce the same effect with the wider range of 1 to 3 inches.

These results are greatly in advance of the best hitherto presented to the Institute.

The fishtail burner, used in the experiments on the regulator No. 2, was detached, and with a variation of pressure from .7 to 1.1 inch, the consumption increased fully 30 per cent. with a further increase of pressure it commenced "blowing," burning with bursts of flame. The photometrical trials showed that this increase of consumption was waste, and this is at least fivefold of that shown in table I. Your committee lay stress upon the point, that this loss is one that cannot be charged to the carelessness

of employés, but that it eludes the eye and can only be completely met by automatic apparatus.

The arrangement of the parts of this regulator is calculated to convey as little heat as possible to the leather diaphragm; and results presented to your committee of leather, said to have been somewhat similarly exposed in twelve months' use, give promise of durability. They have no further guide on this point, or on the possibility of exactly uniform production; but they suggest that, by careful mechanical construction, the principle of these regulators may be rendered effective at lower pressure.

The objects to be tested were arranged in committee, viz: the range of regulation, the advantage of quasi-packing at different pressures, and the ordinary waste with unperceived "blowing." The experiments themselves were made by one of your committee only; they are, therefore, presented only on the authority of its chairman, but your committee unanimously concur in the opinions deduced from them.

Your committee are much indebted to the courtesy and liberality with which the Manhattan Gas company placed their valuable apparatus at its disposal during several hours.

PRESSURES IN INCHES.-A A', a uniform consumption; B B', consumption of Burner No. 1; C C', consumption of No. 2 Burner: D D', consumption of common burner.

The temperature at the time was 82° Fahrenheit.

SELF-REGULATING WINDMILL.

Mr. Enos Stevens presented a plan of a windmill, in which the power is to be regulated by weight; but the plan could be understood only by means of engravings.

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MEASURING THE FORCE OF GUNPOWDER.

The Chairman.-A gentlemen called on me yesterday with a newly invented gunpowder, and in the course of conversation we had a discussion in regard to the mode of measuring the power of powder. I will suggest to the Association this plan: introduce a pipe through the wall of a strong cylinder near its lower end, and, bending the pipe at an elbow, let it rise by the side of the cylinder. Pour some water into the cylinder-more than enough to cover the end of the pipe. Then close the cylinder perfectly tight, with the exception of a hole through the cover, through which a pistol may be discharged into the interior. Will not the force of the powder be measured by the rise of the water in the pipe, the expansion of the gases by the height to which the water rises, and the rapidity of the expansion by the time in which it rises?

Mr. Dibben.-I should doubt the accuracy of this mode. The inertia of the water would cause some time to be consumed in moving it, and during this time the walls of the cylinder would be conducting heat away by convection, diminishing the amount of expansion. I have had a good deal of experience in testing powder with the ordinary eprouvette, and I have found the results with the same samples of powder very variable, and the effect of small charges a very uncertain indication of the effect of large charges. The eprouvette is a small cannon with the bore very accurately turned, and a chamber in the breech to hold a given quantity of powder, generally an ounce. The ball is turned to fit the bore nicely, the charge is weighed and poured into a chamber through a tube, so that it may all go into the chamber, and the breech is made concave to fit the ball, affording no space between the powder and the ball. The cannon is set at an angle of 45°, and the distance to which the ball is thrown is taken as a measure of the force of the powder used. But I have found that two samples of powder taken from the same barrel, and from the same half pound in the barrel, would throw the ball to quite different distances, varying sometimes 20 per

cent. It is found that with the full service charge in large cannon, the range with the same samples of powder is much more nearly uniform.

The Chairman.—The products of the combustion of gunpowder burned under different temperatures are entirely different, and as the temperature varies with the pressure, the force exerted would be affected by the ease with which the shot was moved. This fact suggests the great number of elements which come into an experiment to determine the force of any particular sample of powder, and, consequently, the difficulty of making the investigation.

MODES OF RAISING WATER.

The regular subject of the evening, "Modes of Raising Water," was then taken up.

The Chairman.-I proposed this subject from a selfish motive—the hope of getting some information in relation to it. I shall open it with a few very elementary remarks. Raising water is the same as raising any other substance; the power required is in direct proportion to the weight raised, and the height to which it is raised. The object of most of our devices is to avoid expending power in the production of incidental effects, as the overcoming of friction, etc. The first plan adopted was doubtless that of dipping up the water in a bucket or other vessel, and perhaps this is more economical of power than any other plan that has ever been devised. The amount of friction is inappreciable. When wells were too deep to be reached by the arm, it was necessary to let down the bucket with a rope, and if a large bucket was used, it was found convenient to attach it to a lever with a partially counterbalancing weight at the opposite end of the lever, and thus the sweep came into use. Or the rope was passed over a drum, with a smaller drum on the same shaft for the counterbalancing weight. But when wells were dug in dusty cities, it was necessary to cover them over, and pumps had to be used. These are simply plans for lifting the water, the bucket being made small, and attached to a rod instead of a rope. In this case there is a great increase of friction, requiring a larger expenditure of power. I should like to hear from gentlemen present an account of the more complicated plans that are now employed.

Mr. Fisher. I have a plan for taking water from a ship, which has not been suggested by any one else that I am aware of. It is to run a pipe from the hold of the vessel out of the stern, when the forward motion of the vessel would cause the water to flow out through the pipe. I have made some calculations, which show that a speed of twenty miles an hour would discharge the water under at least four feet head, making a very large allowance for friction, etc.

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Mr. Dibben. The calculations may be all right, but I suspect there would be practical difficulties in the way of arranging the pipes. Ship masters, too, have very strong objections to making holes in the sides of their ships. They are very much disinclined to adopt any alterations in their pumps. I have seen ships within a short time with the pump on the hurricane deck, so that all the water had to be raised twice as high as was necessary. There is nothing that mariners are more afraid of than getting their pumps