and air supplies, and admitting steam into the regenerator tubes. The steam thus passes through the red-hot tubes, then through the combination chamber and its contingent passages, already highly heated, over the articles in the oxidizing chamber, heating and oxidizing them, and thence over the outside of the regenerator tubes, depositing a great portion of its heat there before passing to the chimney, and which is again picked up by the ingoing fresh, cool steam. In this way the heat in the chamber is highest shortly after the commencement of the operation, and gets gradually lower during the time of exposure, which varies, according to the class of goods, from five to ten hours. At the close of the operation, just before the articles are taken out, everything is moderately cool, and this for steam is the perfection of action, as stated by Professor Barff himself. Steel, I consider, can be equally well treated by both processes, and, indeed, it is natural to expect this, steel being, so far as the quantity of carbon it contains is concerned, between cast and wrought iron. Polished steel, however, is better treated in a low-temperature Barff furnace.

With regard to the quality of fuel burned in the gas-producers, a non-coking gas coal is the best, and Virginia splint has suited very well in this country; and of this about 1 ton every three days is required for a furnace with an oxidizing chamber 13 feet long, 4 feet 3 inches wide, and 4 feet 3 inches high. When a gas coal is employed it should be fed through the charging hoppers just before each deoxidizing operation, when a smoky flame is of great advantage. I have, however, dis. covered that anthracite can be used as well as a gas coal, by simply allowing petroleum to drop at the rate of 1 gallon per hour upon the red-hot surface of the coal in one of the gas-producers. This method has been exclusively used in the coating of the articles treated at the works of Messrs. Poulson & Eger, architectural engineers, at North Eleventh and Third streets, Brooklyn, E. D., New York, to whom I am much indebted, not only for these beautiful castings, but for the constant courtesy and energy they have always exhibited during the erection of their furnaces. At present they have two erected, one a Bower furnace of the size before mentioned, and the other a small Barff furnace for the treatment of very delicate or polished articles. These magnetic-oxide processes not only protect from rust, but the coating is of such a beautiful color as to render articles ready for the market as soon as they are out of the furnace and cooled. One remarkable feature of them is that there is no more cost (except in the labor of handling them) in treating 2,240 articles, each weighing a pound, than there is in coating a cube of metal weighing a ton, and so penetrating is the process that, no matter how intricate the pattern may be, every crevicewhich it would be almost impossible to get at with a paint brush—is as effectively coated as the plainest surfaces. For art purposes the French gray color, with shades approaching to black, might not always be suitable; but if it should be necessary to use paint on the iron so coated, there

is the absolute certainty that it will remain on in the same way as it does, on wood or stone, and thus iron may be used for constructive work in a thousand directions in which it has not up to the present time been possible, on account of its liability to rust, no matter what the coating used to protect it has been.

I can give an instructive instance of this. A company in Paris had expended a very large sum over Dode's inoxidizing process, which process consists in the depositing of a layer of borate of lead on iron or steel, and then gilding, platinizing, or bronzing them, and certainly the articles so treated were exceedingly beautiful to look at; but the iron ultimately rebelled and threw off the coating, so that the shareholders were in a fair way of losing all their capital, when it was suggested to the directors that if their compositions could be deposited direct upon magnetic oxide they would conquer the difficulty. They then applied to my father for specimens of coated iron to experiment upon, and they were so satisfied with the result that the company purchased all our European patents except for England, and are carrying on the combined processes on a large scale. They have, besides their furnaces for the Dode process four large Bower ones, two being 36 feet long by about 6 feet 6 inches wide and 6 feet high, and a Bower-Barff furnace, also of large size. Others, however, are in course of erection.

Engineers and manufacturers appear far more ready to apply the processes here and on the continent of Europe than up to the present time they have been in England; but perhaps the reason has been that so far as Professor Barff's process is concerned it has only just been shown how large masses can be dealt with-namely, by the use of the Bower furnace and I can show that for the treatment of underground pipes, wrought-iron sleepers, roofing, and the like, the process can be readily applied, and at a cost much less than that of galvanizing, and it will at the same time be infinitely more durable; while for ornamental cast and wrought iron it is scarcely possible to imagine anything more artistic in color than some of the articles after they have been treated. For ordinary hollow-ware for kitchen use, whether of cast or wrought iron, this process is admirably adapted, and though I have been told that the gray or black color will probably be objectionable, yet I imagine if it can be shown, as we can do, that the magnetic oxide is more durable, more easily cleaned, and much cheaper than even the common tinted article, a market will soon be created. Anyhow the new combined processes are so far developed, and they have been so thoroughly examined by scientific and practical men both here and in Europe (whose testimony to the value and efficacy of them is voluminous), that they have passed from the region of theoretical investigation into that of practical application, and means have been taken for establishing works in different centers in Europe, as will also be done here, for the purpose of coating iron and steel as a trade operation. One firm alone in Scotland, Messrs. Walter Macfarlane & Co., have adopted the process, their output of ornamental castings per day exceeding 100 tons. It is intended

to apply the process to cast-iron gas and water pipes, and, as the for mer have comparatively no pressure to bear, they may be made much lighter than they now are, if rendered incorrodible; while for water it will be a great advantage to have both the main and service pipes rendered safe from rust, which not only discolors the water, but forms the nucleus of very troublesome deposits. There is no reason now why wrought-iron or mild steel pipes should not be used for the same purposes, especially for the interior towns of distant countries, where the first cost of the pipes is but small as compared with the cost of carriage. My father has himself used gas and water pipes where the cost on arrival at their destination has been five times greater than their first cost in England. If, then, light wrought-iron or steel pipes could be used, not weighing one-third of those made of cast iron, and rendered practically indestructible, an enormous saving will be effected. Again, in the case of railway sleepers in iron and steel, which are now almost wholly used in Germany, the process is likely to prove of much advantage, so at least I am told by engineers both in Belgium and in Germany; and if there why not here? For fountains, railings, and all architectural work the process is invaluable, and iron may now be used in many instances instead of bronze. It will naturally be asked, what is the cost of the process? I cannot do better than answer the question by quoting from the report of Professor Flamache, the engineer-in-chief of the State railways in Belgium, who was sent over specially to England to report on the process by the public works department of that country. His estimate of cost, after a very careful examination and testing of the process, was 7 francs per 1,000 kilograms, or nearly $2 per ton, at, of course, the Belgian rate of expenses. He also gives the cost of coating a certain extent of surface, but this I consider to be completely valueless, as, for example, I have had a furnace full of 56-pound weights, and another time I have had it full of gas-governor tops, the surface in the latter case being perhaps one hundred times more in extent than in the former, while the actual cost of oxidizing would be the same in both cases. He also says that this cost may be reduced, as instead of one workman attending to one furnace, he can attend to three or four; also by a better system of taking the articles out than existed in the experimental furnace that he saw. Sir Joseph Whitworth, feeling much interest in Professor Barff's process, sent to him some steel to be oxidized, so that he might ascertain whether it did or did not lose in strength by the operation, and the result of Sir Joseph's testing was that there had been no alteration whatever. Theoretically, one would rather expect that iron and steel would be somewhat toughened, as the tendency of the process is to anneal, and would, no doubt, if continued long enough, render some classes of cast iron malleable. A very thin article, if excessively coated, might probably be weakened, due to the fact that the coat of magnetic oxide would form an appreciable percentage of the bulk of the article; but this, of course, is a very extreme case, and one which is not likely ever to occur in practice.

GOLD AND SILVER.

Limited scope of the discussion.-The act of Congress providing for the collection and publication of mineral statistics under the auspices of the United States Geological Survey restricted the field to mineral products other than gold and silver. No attempt, therefore, has been made in the way of original investigation of this very important branch of the mining industry. In order, however, to present as complete a view of the total mineral output as possible, the best available figures of the production of the precious metals are here presented in a concise form.

Production in 1881 and 1882.-The following table shows the yield of gold and silver in the United States during the calendar years 1881 and 1882, as estimated by Hon. Horatio C. Burchard, Director of the Mint; and these results are accepted authoritatively in further computations in this report. The figures for 1882 have been kindly furnished in advance of their publication by Mr. Burchard. The amounts are stated at the coining value, the actual market price of the silver being considerably lower than the figure given, while in the case of gold the actual net receipts by the miners are also slightly under the nominal value, owing to the large amounts of placer gold which are sold by them at a small discount.

Production of gold and silver in the United States during the calendar years 1881 and 1882.

Rank of the States and Territories in 1882.-The relative production of gold and silver, and of both metals combined, in the several States and Territories is perhaps more clearly shown in the following statement, in which the order of the States and Territories according to their respective outputs is based on the figures given by Mr. Burchard for 1882:

Rank of the States and Territories in the production of gold and silver in 1882.

Production in first six months of 1883.-Mr. R. E. Preston, Acting Director of the Mint, in answer to a request for his estimate of the production during the first six months of the calendar year 1883, writes, under date of June 13, 1883: "The production since January 1, 1883, has continued at about the same rate as in 1882. In some States and Territories there has been a slight increase, and in others a trifling decrease; but the average rate can be said to have been maintained." The opinion of the mint authorities may be accepted as being the most reliable guide in the absence of actual statistics for the first half of 1883, which of course have not yet been collected. The following statement shows the quantities as well as the values of the product of 1882, and also the corresponding estimated amounts for the first half of 1883; the weights of metals being computed from the values quoted, on the American standard of $20.671834 per troy ounce gold, and $1.2929 per troy ounce silver:

Quantities and values of the precious-metal product, 1882 and first six months of 1883.