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purchase vignetting plates ready-made is by no means satisfactory, as pictures vary extremely as regards the kind of opening which is likely to suit. Feilner’s system of making vignetting plates, patented about a year ago in Germany, and described in Liesegang’s Archiv, will probably be found useful to those photographers who desire to obtain as good vignettes as is possible from each particular negative, and results which shall be absolutely uniform for all pictures taken from the same negative. A series of paper shades are gummed on glass plates, as represented by figures 1 to 5, care being taken that the papers are so mounted on the glass that, when the plates are superimposed, the paper shades shall, if considered collectively, form a kind of funnel-shaped figure as repre ¬ sented by fig. 7. It is generally desirable to use an additional shade made of black paper (fig. 6.), in order to insure complete opacity. The series of shades are next mounted in a kind of copying camera arrangement, which is represented by the subjoined block, the plates being y4 i—— 1 1 ।» 1— er .5-i- 20 do 40 50 - 60 70 05 arranged as represented in at E, a single thickness of finely- ground glass being placed at each end of the series. The work of photographing the gradated image, and thus making a vignetting plate, requires no special Comment; and it is obvious that either a positive or a negative can be obtained at will by reproducing the first photograph; or, if preferred, the same end can be obtained by either work ing from masks or discs, as the case may be, in the first instance. Fig. 8 gives some notion of a special form of opening, such as may occasionally be required. It is obviously possible to obtain artificial cloud nega tives by a somewhat similar proceeding, GLASS. Fifth Article. In every process or manufacture in which great heat is used, the furnace and its construction become matters of most vital consequence, so much depending upon its suitability and economy of fuel, as well as upon its dura bility, needing few repairs, combined with a moderate outlay for its first cost. In a few short articles, such as the present, it is quite impossible to treat of matters of minute detail, otherwise the bulk of a year’s issue of the NEWS might easily be devoted to the subject of furnaces, heat in its various methods of application, and so on. When we consider that heat (one of the most potent agencies employed by man) forms the basis and ground work of every process of manufacture, even to the making of ice, and is, as Tyndall has it, a “ mode of motion ” ; that the sun (according to Proctor only 100,000,000 years old) has stored up our present coal fields, and quickens the herbage upon which our beef and mutton is reared, and whence we derive the motion requisite to drive the quill that pens these lines, or set up this type ; when we reflect that it is the same heat which hardens clay and melts gold, and is, in fact, an excellent servant but a terrible master, we may well devote a chapter to furnaces and heat appliances as far as concerns glass-making. We have already hinted that glass manufacture, as carried on in England, differs from that of Belgium. It is from no want of a robust feeling of patriotism that we say unhesitatingly that the English system is wrong, inasmuch as it is laborious, costly, and less scientific than that of Belgium ; therefore we elect not to waste our space by useless descriptions of what is old-fashioned or behind the age, and so we forthwith give a sketch of the furnaces actually in use at the present day in Belgium. This sketch is a sectional drawing, taken through the centre of the pots ; it shows almost without description what is the exact construction, for it has been very neatly reproduced by our engraver, and we may remark that probably in no published work is there to be found a drawing in section of a Belgian furnace which shows so clearly the whole affair at a glance. A few words of explanation may render the drawing doubly intelligible. A Belgian pot furnace, for use with coal. The visitor to the glass-making district of Belgium situ ated around Charleroi and Lodelinsart would be very