of 340 per second, was ninety-four billionths of a second (000000094); still, on experimenting, it was evident that the duration of the discharge was less than this quantity, as the lines were always plainly to be seen. Duration of the first act of the discharge. Before finally abandoning the attempt to determine the actual duration of the discharge, another effort was made; second lamp-black plate was prepared, in which the breadth of the image of a line, black or white, on the observing plate was of of a millimeter. These lines were viewed with the terrestrial eye-piece of a small telescope; it enlarged them ten diameters, and care was taken with all the adjustments so that a good clean image should be produced. Platinum wires an inch in diameter were used with a striking distance of five millimeters. By gradually increasing the weight, it was proved successively that the duration was less than eighty, sixty-eight, fifty-nine, fifty-five billionths of a second; and finally, the lines after growing fainter and fainter, entirely disappeared, giving as the result a duration of forty-eight billionths of a second. In a large number of observations I could detect no discharge lasting during a smaller interval, though the apparatus was now fully capable of making evident much smaller periods of time. When the striking distance was reduced to one millimeter, the duration was shorter; in the case of of the sparks, the duration was slightly greater than forty-one billionths of a second, the remaining being slightly less than this figure. With a striking distance of three millimeters, the duration was between forty-one and forty-eight billionths; and when the striking distance was increased to ten millimeters, it was between forty-eight and fifty-five billionths of a second. An effort was made to make a corresponding set of measurements with brass balls instead of platinum points; and it would seem probable that the duration of the discharge is somewhat increased by their use (or that many of those with shorter durations are suppressed). With brass balls not nearly so many discharges take place in a given time as with points; hence, the work becomes tedious and less certain. The evidence from twenty-six observations, gathered in not less than three hours, went to show that the duration with a striking distance of five millimeters was between forty-eight and fifty-five billionths of a second. It has thus been shown that the duration of the first act of the electric discharge is in certain cases only forty billionths of a second, an interval of time just sufficient to enable a ray of light to travel over forty feet. This act, however, is only practically isolated; from a scientific point of view it is really the distance 3 1 A B, fig. 3, which has been measured; and as we are ignorant of the true curve, it might be objected that the real curve might just as well be supposed to be like that given with dotted line. There is, however, experimental evidence to show that this is not the case; for on this supposition, the blurring of the image would begin to be visbile far earlier, i. e., with lower velocities than has been observed. In point of fact, the image remains visibly as distinct as with a stationary mirror till a certain stage, when it begins to be affected, becomes regularly less distinct, and vanishes; between this stage and the final disappearance, there is included an interval of time which is barely accounted for by the gradual superposition of the white and black lines, as I assured myself by parallel experiments with revolving discs, provided with black and white sectors, and an observing aperture of varying size. Hence it is seen that we have an excellent source of illumination, which has a practical duration of only forty billionths of a second (00000004); and I am not without hope that it may hereafter be applied to the solution of a number of interesting scientific problems. I may finally add that with another ruled plate, I found it practicable to measure intervals as small as twenty-eight billionths of a second; and the mere act of increasing the focal length of the lens L would admit of the experimenter reaching a quantity as small as ten billionths-probably without much difficulty-though it would be necessary to pay more attention to the correction of the optical part of the apparatus, and the observations would naturally consume threefold as much time. Duration of the first act, with a Leyden jar having a coating of 114.4 square inches. With the improvements above described, no difficulty was experienced in making this determination, which, as shown in Part First of the present paper, had on a previous occasion defied all my efforts. Platinum points and a striking distance of two millimeters were employed in connection with the coarsest of the three lamp-black plates; but when the mirror made only 183 turns in a second, it was ascertained that the duration of this first act was 000000175 of a second, or about four times as great as with the small jar and the same striking distance. New York, June 29th, 1871. ART. XXIV.-Memoranda concerning the introduction of the h Manufacture of Spelter into the United States; by JOSEPH WHARTON. תי SPELTER, as crude metallic zinc is called in commerce, had it never before the year 1859, been produced in America upon such terms as to give hope of its manufacture becoming a settled industry in this country. Mr. John Hitz in 1838 made enough zinc from the ores of the New Jersey Zinc Co., to supply material for a set of standard U. S. weights and measures in brass, but the quantity produced was small, and the cost extremely high. The Lehigh Zinc Co. caused to be erected in 1856 a spelter furnace at their mine near Friedensville, Pa., upon the Silesian plan; this furnace, though apparently well constructed, failed to yield any zinc, mainly because its builder, Mr. Charles Hoofstetten, was unable to make or to procure any suitable muffles. Mr. Samuel Wetherill, the patentee of some valuable improvements in the manufacture of zinc oxide, also experimented in a spirited manner upon the production of metallic zinc, and actually produced some at South Bethlehem, Pa., as early as 1858, but though he persevered for about two years, and made a considerable quantity of excellent spelter-in all I think about 50 tons-the cost price was too high, and his enterprise was finally abandoned.* Some other endeavors of less significance were also made which need not now be mentioned; sundry details relating to the early American history of spelter-making may, however, be found in the New American Cyclopedia under the head Zinc, vol. xvi, pp. 636 and 644. The present paper proposes to give some particulars, which even at this late day may possess interest, concerning that attempt to produce spelter in this country which really succeeded in establishing the industry here, upon such a footing as to enable it thenceforth to take even rank with other American manufactures in their struggle against European competition. Having acquired some practical knowledge of the properties of zinc, by several years experience as general manager of the Lehigh Zinc Co's. mines and zinc oxide works, and having also gathered such information as was possible from books and other sources, I made various trials during 1857 and 1858, to invent some form of furnace which should effect the evolution and condensation of zinc vapor in a larger and more continuous way than was practised in Europe, and which should thus *The first sheet zinc made in America was rolled by Alan Wood & Sons of Philadelphia, from an ingot of Mr. Wetherill's spelter. T fulfill in a simpler and more scientific manner, what seemed to be the easy theoretical conditions of the problem. Some of these attempts were not devoid of ingenuity; they cost me much toil and money, but they all failed utterly, by reason of my having overlooked one or another of what may be called the conditions of secondary importance. They served very little purpose but to instruct me in the real difficulties of the manufacture, and I revert to them now mainly to point out to my younger or more sanguine readers that it is usually very bad economy to labor over the rudiments of an art which is to be transplanted, repeating perhaps, many futile unpublished experiments of its founders, when it is at all practicable for them to adopt the processes successfully used elsewhere. In the year 1859, abandoning these original flights, I built for the Lehigh Zinc Co., at South Bethlehem, Pennsylvania, a single spelter furnace of about 45 retorts, upon the Belgian plan and by the aid of several Belgian workmen imported for the purpose. Since it was necessary for permanent success that only conveniently accessible and cheap American materials should be used, the fuel employed was exclusively Pennsylvania anthracite, the retorts and condensers were made by ourselves, mainly from the fire clay of Perth Amboy, New Jersey, and the ore was hydrous silicate of zinc, from the Lehigh Zinc Co.'s mine near Friedensville, four miles south from Bethlehem, Pennsylvania. This experiment was continued for several months, and was divided into five periods or campaigns. After its close I furnished to the Lehigh Zinc Co., in September, 1859, a report, from which the figures below are extracted; these give the average results of the last three of those periods, and show the expenditures calculated to the 1000 lbs. of the spelter produced. The price of ore was here assumed at rather more than the cost of mining and hauling to the furnace; the price of coal was that actually paid for the small sizes employed, then relatively less valued than now; the wages were of course high, because but a single furnace was operated, and we were learning, viz: 4,304 lbs. raw zinc ore at $2.50 per 2,240 lbs., - Steam power, Rent of buildings,. (Superintendance, office expenses, &c., not counted), Total cost of 1,000 lbs. Spelter,..... $ 4.80 6.11 20.45 1.75 6.00 1.00 60 $40.71 The entire cost of this experiment, including the importation of workmen, construction of furnace and tools, and all collateral expenses was $3,795.89. The quantity of spelter produced was 34,063 lbs. a That report naturally excited in the minds of the Lehigh Zinc Company, a strong desire to engage at once in the manu- a facture of spelter, since not only were the technical difficulties in the way of this great prize overcome, and the product of excellent quality, but the cost was within the market price, and there were apparent margins for economizing in several particulars. On the other hand doubts naturally lingered as to the possibility of attaining the expected results upon a large scale, and the financial position of the Company was at that fa time such as to enforce caution. Both funds and courage were in fact rather lacking, and though I made various propositions, including one to build the desired factory at my own cost, tak ing pay in a reduction in the price of ore which I would buy to treat in the factory on my own account, no satisfactory arrangement could be immediately made. Ultimately, however, an agreement was entered into between that Company and myself, on the 13th of December, 1859, by which I engaged for the sum of $30,000, to convey to them a suitable piece of ground in South Bethlehem, Penn., and to erect thereupon by July 1, 1860, a complete Spelter Works, of sixteen Belgian furnaces, each containing fifty-four working retorts; the furnaces to be enclosed in a suitable stone or brick building with slate roof, 155 feet long and 40 feet wide; the establishment to be provided with steam engine and boilers, steam pump drawing water from the Lehigh river, blowers, orecrushing mill and store room-all these latter to be enclosed in a suitable stone building with slate roof-also to be provided with pottery fully equipped with clay mills and apparatus to make all fire bricks, retorts, condensers, etc., needed in the business, ore-roasting furnaces, air flues and water pipes, railroad into yard, coal bins, etc., and to be in all respects capable of making from the Lehigh Zinc Co.'s selected or lump ores 3,000,000 lbs. of spelter annually. I also bought from the Company 15,000 tons (of 2,352 lbs. each, moist weight) of their selected ore at $7 per ton for the first 5,000 tons, $7.50 per ton for the second 5,000 tons, and $8 per ton, for the third 5,000 tons; the average of which prices was calculated to equal the average price which had been theretofore received for several considerable lots of similar ore, sent by the Company to England. I also agreed to rent the factory to be built as above mentioned, from July 1, 1860 until Jan. 1, 1863 at $3,000, per annum, and at the end of that period to hand it over to the Lehigh Zinc Co., in complete running order for producing the stipulated 3,000,000 lbs. of spelter annually. |