IT NOTE UPON THE "BLUE" PROCESS OF COPYING TRACINGS, ETC. BY P. BARNES, PLAINFIELD, N. J. (Read at the Philadelphia Meeting, February, 1878.) may be of interest, and perhaps of importance, to the members of the Institute that specific mention should be made in detail of the great value of this method of copying or photographing all kinds of tracings.* Several samples are laid upon the table which may serve as illustrations of the results obtained. Some of these show slight imperfections, depending upon the character of the tracing, and upon the length of the exposure to the light, but it may be clearly seen that even a faint copy would be quite available for actual use. The process is believed to be of French origin, and has been used for many years. Special attention seems to have been directed to it recently, and its great value to engineers appears likely to be fully recognized. The manipulations required are of the simplest possible kind, and are entirely within the skill and comprehension of any office boy who can be trusted to copy a letter in an ordinary press. These particulars may be summarized somewhat thus: 1. Provide a flat board as large as the tracing which is to be copied. 2. Lay on this board two or three thicknesses of common blanket, or its equivalent, to give a slightly yielding backing for the paper. 3. Lay on the blanket the prepared paper with the sensitive side uppermost. 4. Lay on this paper the tracing, smoothing it out as perfectly as possible so as to insure a perfect contact with the paper. 5. Lay on the tracing a plate of clear glass, which should be heavy enough to press the tracing close down upon the paper. Ordinary plate-glass of 3" thickness is quite sufficient. 6. Expose the whole to a clear sunlight, by pushing it out on a shelf from an ordinary window, or in any other convenient way, for six to ten minutes. If a clear skylight only can be had, the exposure must be continued for thirty or forty-five minutes, and under a cloudy sky, sixty to ninety minutes may be needed. * The introduction of this process into the United States is due principally to Mr. A. L. Holley, who first drew the attention of American engineers to its simplicity and convenience. Mention was also made of the process at the meeting of the Institute in New York, in February, 1877, by Mr. Ogden Haight. 7. Remove the prepared paper and drench it freely for one or two minutes in clean water, and hang it up by one corner to dry. Any good hard paper may be employed (from even a leaf from a press copy-book up to Bristol board) which will bear the necessary wetting. For the sensitizing solution take 13 oz. citrate of iron and ammonia and 8 oz. clean water; and also, 14 oz. red prussiate of potash and 8 oz. clean water; dissolve these separately and mix them, keeping the solution in a yellow glass bottle, or carefully protected from the light. The paper may be very conveniently coated with a sponge of four inches diameter, with one flat side. The paper may be gone over once with the sponge quite moist with the solution, and a second time with the sponge squeezed very dry. The sheet should then be laid away to dry in a dark place, as in a drawer, and must be shielded from the light until it is to be used. When dry the paper is of a full yellow or bronze color; after the exposure to the light the surface becomes a darker bronze, and the lines of the tracing appear as still darker on the surface. Upon washing the paper the characteristic blue tint appears, with the lines of the tracing in vivid contrast. It will readily be seen that the process is strictly photographic, in the ordinary sense of the word-the tracing taking the place in the printing of the ordinary glass negative. Hence all details are closely reproduced, even to the texture or threads of the tracing-cloth. A working drawing thus made furnishes its own background, and does not require to be placed over a white ground, as is often the case with a tracing. If desired the copy can be made upon common bond paper, which can be mounted upon a board in the usual way. Inasmuch as such copies can be made from tracings only, it may be well to suggest, and urge, that drawings can be completed or nearly so in pencil upon paper in the usual way, and that all the inking can be done upon tracing-cloth laid upon the pencil-work. In this way the cost of the tracing (in the ordinary sense) can be wholly saved, and the single copy of the finished tracing can thus be made in the "blue" way to the best possible advantage. It may safely be said that this method of copying can be employed if only one or two copies per week are needed of ordinarily complex drawings, with excellent results and with a very important saving of time and money. A ready means of adding to or correcting the blue copies may be found in the use of a solution of carbonate of soda or potash, used with a pen or brush. February 23d, 1878. THE ECONOMY EFFECTED BY THE USE OF RED CHARCOAL. BY B. FERNOW, BROOKLYN, N. Y., LATE MEMBER OF THE PRUSSIAN FOREST DEPARTMENT. (Read at the Philadelphia Meeting, February, 1878.) THE question of preserving the forests in this country is an important one, not only to trades using wood but to the whole nation, and though agitated for many years has not received that general consideration which its broad bearing demands. Those who are interested in and working for reform in the treatment of American forests are looking to the government for help, suggesting the creation of a commission to study the conditions of forests at home and abroad, and hope that a sound system of managing the woodlands will be thereby inaugurated. This reform will cost time and money, all the more because the government can bring to bear upon private owners hardly any power but that of good example and encouragement. There is, however, another aspect of the question to which I wish to draw your attention, namely; the more economical use of the valuable material which our forests offer, a more careful and exhaustive utilization of its constituents in all cases where wood or its products are applied. The wasteful consumption of wood in the United States is in every way so enormous as to justify the statement that by merely adopting an economical husbandry in this particular the destruction of forests might be delayed for many years, while the neglect of this imperatively needed and immediately practicable reform deprives legislative remedies of much of their value. In this regard I wish to draw the attention of metallurgists, especially those who are interested in the manufacture of charcoal iron, to a more economical and profitable use of wood in iron manufacture. For thousands of years of human history wood was the main, nay, the only material used for fuel. Mineral coal came into use only in the fourteenth century, and it is only recently that it has largely displaced its less carbonaceous predecessor as fuel. The art of concentrating carbon in the form of charcoal for easier transportation and readier use in distant places was, according to Pliny, known to the ancients long before Christ, and was practiced in all countries, especially in connection with the iron manufacture. Nevertheless, important as the material and extended as its use has been, hardly any progress has been made in developing the art of charcoal-making down to the present time, and the charcoal-burner of to-day is scarcely in advance of his predecessor of two thousand years in the method of treating wood to obtain a better and larger yield. Of course attempts have been made to bring the process to a more scientific basis, but all the improvements have not amounted to enough to give perfect control of the process to the burner or to secure a larger yield of empyreumatic products. "Meiler "charring (or, as it is called in this country, burning in pits), with its dependence upon weather and good luck, its uncertainty of a long period of burning, and many other inconveniences, it is still claimed, gives the best results, and only reasons outside the process itself have led to the more general use of kilns, which are said to give a weaker charcoal and a smaller yield. To economize in another direction, namely, by collecting the byproducts lost during the process of meiler-charring, various contrivances have been proposed. Some of these are employed with good effect, though not without injury to the final product, the charcoal, which generally is rendered less valuable by such processes. In this country so far as I can ascertain no pains are ordinarily taken to utilize these by-products, though it would be easy to do so, since the use of kilns, which facilitates the collection of the by-products, is more common here than in the old countries. But, as above remarked, in operating for these by-products the main product, charcoal, is generally neglected and it is mostly of a weaker quality. The general results obtained by the manufacturers who distil wood with the greatest precaution in closed vessels, and who have in view the utilization of all the products resulting from the operation, may be expressed for 100 parts of wood, thus: Carbonic acid and carbonic oxide, hydrocarbons and If to these numbers be added the fuel to effect the distillation, about 12 weight of wood necessary as parts, the results will agree well with what is arrived at in burning for charcoal. These results agree pretty closely with those of theoretical calcu |