Popular Science Monthly/Volume 46/March 1895/Copper, Steel, and Bank-Note Engraving
| COPPER, STEEL, AND BANK-NOTE ENGRAVING. |
By C. W. DICKINSON.
HOW few of the many people who are fortunate enough to have a dollar bill in their pocket think of it as a work of art! Two hundred years ago this piece of paper would have been of almost incalculable value, and have awakened an interest among the artists of that day which we can scarcely realize. Look at the portrait on the left of the face of the note. Here we have a beautiful specimen of pure line engraving—much better work than most of that done by some of the old masters and now considered classic. Then there are on both face and back the fine, delicate effects of light and shade produced by the ruling machine and geometrical and cycloidal engraving lathes. Further than this can be seen elegant designs in scroll work and lettering.
This may be a piece of "the root of all evil," and we know it is often "filthy lucre," only worth one hundred cents to us, yet it may be profitable to inquire as to how it is made.
Steel and copper plate engraving does not, as is generally supposed, owe its origin to the woodcut, but to the chasing on goldsmith's work. Look at any article of jewelry ornamented with incised designs, and there will be seen the true origin of line engraving; and although this work was not done—as was the steel or copper plate engraving—for the purpose of producing copies by printing, still it was by this engraving on jewelry that the art of printing from an incised line was, like a great many other good inventions, accidentally discovered.
The goldsmiths of Florence, in the middle of the fifteenth century, were in the habit of ornamenting their works by means of engraving, after which they filled up the hollows produced by the graver with black enamel (made of silver, lead, and sulphur, the result being that the design was rendered much more visible by the contrast of the enamel and the metal.
An engraved design filled up in this manner was called a niello, and our modern door plates are really nielli also, for in these, too, the engraved lines are filled with black. The word niello comes from nigellum, and simply refers to the color of the enamel.
While a niello was in progress, the artist could not see the effect of his work so well as if the enamel were already in the lines; and, on the other hand, he did not like to put the enamel in the unfinished engraving, as, when once it was set, it could not easily be got out again. He therefore took a sulphur cast of his niello—in progress—on a matrix of fine clay, and filled up the lines in the sulphur with lampblack, thus enabling himself to judge of the effect of his engraving thus far.
At a later period it was discovered that a proof could be taken on damp paper by filling the engraved lines with a certain ink and wiping it off the surface of the plate, sufficient pressure being applied to make the paper go into the hollowed or engraved lines and bring the ink out of them. This was the beginning of plate printing, but nobody at first suspected the artistic and commercial importance of the discovery. The niello engravers thought it a convenient way of proving their work, as it saved the trouble of the sulphur cast, but they saw no further into the future. They went on engraving niello just the same, to ornament jewelry and furniture; nor was it until the next century that the new method of printing was carried out to its great and wonderful results. Even in our day the full importance of it is only understood by persons who have made the fine arts a subject of special study.
The earliest engravers on metal for the purpose of multiplying by printing, of which we have reliable information concerning names and dates, were the German artists, Martin Schongauer and Albert Dürer. Schongauer was the earlier artist of the two, as he died in 1488, while the date of Dürer's death is 1528, just forty years later.
Schongauer, though a generation before Dürer, was scarcely inferior to him in the use of the graver, but Dürer has a much greater reputation—due in a large measure to his singular imaginative powers. Schongauer is the first great engraver who is known to us by name, although he was preceded by an unknown German master who is called "the Master of 1466." He had Gothic notions of art, but used the graver skillfully in his own way; conceiving of line and shade as separate elements, yet shading with an evident desire to follow the form of the thing shaded, and with lines in various directions.
Schongauer's art is a great stride in advance, and we find in him an evident pleasure in the bold use of the graver; his outline and shade were better blended, the shade being done more by the use of curved lines than is found in the works of those before him.
Dürer continued Schongauer's curved shading with increasing delicacy and skill, and as he found himself able to perform feats with the graver which amused both himself and his buyers, he overloaded his plates with quantities of living and inanimate objects, each of which he finished with as much care as if it were the most important thing in the composition.
The engravers of those days had no conception of any necessity for subordinating one part of their work to another; they drew—like children—first one object and then another, and so on, until the plate was furnished from top to bottom and from right side to left.
In Dürer, all objects are on the same plane! In his Saint Hubert, the stag (Fig. 1) is quietly standing on the horse's back.
Fig. 1.—Dürer's Saint Hubert.
with one hoof on the saddle, and the kneeling knight looks as if he were tapping the horse on the nose while bowing before the crucifix. The artist seems to have noticed the mistake about the stag, for he put a tree between us and the animal to correct it, but the stag is on the horse's back nevertheless.
There is no reason why steel engraving should be used only to translate painting. The early engravers were often original artists who worked out designs of their own, but in course of time a commercial reason prevailed over originality. It was found that a well-known painting assured the sale of an engraving from it beforehand, whereas an engraving which stood entirely on its own merits came into the world without advantages, and had its own way to make. Besides this, the engraver who copied a picture saved himself all the trouble of thinking out and composing the design which he found ready to his hand.
This is why we have to-day so very few original artists in steel engraving and etching; although there has been a great revival of etching in the last twenty years, especially in Europe, and many artists have acquired great skill in this mode of engraving (Hayden in Europe and James D. Smillie in America being considered the best in their respective countries), it has nearly all been copying.
We can not but deplore this subordination of engraving to painting, and when we look back to the great engravers of past times, who composed and invented their own works, it is with a feeling of regret that they have left so very few successors; for steel engravings have found a place in the hearts of the people of this country that no other class of art can ever replace.
Before leaving this subject of early engravers and their works, let us look at the influence exerted upon them by Raphael and Rubens.
In Italy, Marc Antonio was considered one of the great artists and copied Dürer, translating more than sixty of his woodcuts in metal (for Dürer was also a wood engraver).
It is one of the most remarkable things in the history of art that a man who had trained himself by copying northern work—little removed from pure Gothicism—should have become, soon afterward, the great engraver of Raphael, who was much pleased with his work and aided him by personal advice. Yet, although Raphael was a painter and Marc Antonio his interpreter, we must not infer that engraving had as yet subordinated itself to painting.
Raphael himself evidently considered engraving a distinct art, for he never once set Marc Antonio to work from a picture, but always gave him drawings, which the engraver might interpret without going outside of his own art; consequently, Marc Antonio's works are always original engravings. A school of engraving was thus founded by Raphael through Marc Antonio, which cast aside the minute details of the early schools for a broad, harmonious treatment.
Another school—which marked a new development—was known as the engravers of Rubens. That great painter understood the importance of engraving as a means of increasing his fame and wealth, and directed Vorsterman and others, as Raphael had directed Marc Antonio. Rubens's theory of engraving was that it ought not to give accurately the local color of the picture, which would appear wanting in harmony when not associated with the hues of the painting; and it was one of his anxieties so to direct his engravers that the result might be a fine plate independent of what he had painted. To this end he also helped his engravers by drawings, and he sometimes went so far as to indicate what he thought the best direction for the lines.
Previous to the year 1830 only copper plate was used by engravers, because up to that time it was not thought possible to make steel soft enough to cut easily and smoothly. The first plate produced—that could be used—was called "silver steel." Later there was manufactured the "Prussian steel" plate, which was a slight improvement in fineness of grain. Other and greater improvements followed, until now steel has almost entirely superseded copper.
Decarbonated cast steel is used for general engraving purposes and must be of very fine grain, and very soft as compared with natural cast steel. The plates are rolled out from bars of steel in its natural state, then decarbonated and cut to about the size desired, leaving enough margin to square the edges, which are finished with a wide bevel. After the plate has been cut to size, it is flattened by laying it upon a copper anvil and hammering with a wooden mallet until it is as flat as is possible to get it by that process. A uniform thickness and perfectly flat surface are then given to the plate by grinding—sometimes by hand, usually by machine—the latter process being the better, as it is the more perfect in its results. By grading the stones used in this grinding from coarse to fine, the plate is left ready for the final finish, which is given by burnishing and rubbing with very fine emery leather made for the purpose, from the finest grade of emery that can be had.
Copper plate is still used to a considerable extent for visiting cards, invitations, and such small work as calls for only a limited number of impressions, for copper will not stand nearly as much wear as steel, often wearing out in one thousand impressions, while ten or even fifteen thousand can be taken from steel, and, if the plate is hardened, as is often done, one hundred thousand have sometimes been pulled before the plate has entirely given out. Copper is also used in some cases for the cheaper classes of picture work, such as book illustrations, but it is usually coated with steel or nickel by precipitation, this facing taking the wear instead of the copper.
The tools used in steel engraving are about the same as those used on wood, excepting the heavier wood scaupers, as they are called (chisels or gouges would perhaps give a better idea of what they are). These could not be used on steel, because the hand of the artist could not force them through the line to be cut; so a more delicate graver is used, and a great many cuts are taken in the same line, thus making it broader and deeper by degrees.
There are several kinds of picture engraving and etching, the most prominent of which are aquatint, mezzotint, stipple, rouletting, and line engraving.
Aquatint is a kind of etching used to get the effect of drawings in India ink, and at one time it was greatly made use of in rendering the drawings of Paul Sandby and our early water-color painters, and particularly prints for drawing-books.
There are many ways of preparing a plate for this work, but the following is the best: Have three different solutions of rosin in rectified alcohol, making them of various degrees of strength, but always thin enough to be quite fluid, the weakest solution being almost colorless. First pour the strongest solution on the plate, which has previously been very carefully cleansed from all oil and grease that would prevent the acid acting upon the steel. When this strongest solution dries it produces a granulation, and you may now bite or corrode the steel with acid through these granulations for your darker tones, stopping out with a varnish made of sealing-wax dissolved in alcohol where the acid is not to operate, or the acid may be applied with a brush where the dark tones are desired. After cleaning the plate as before you proceed with the weaker solutions in the same way; the weakest giving the finest granulations for skies, distances, etc.
The process requires a good deal of stopping out and some burnishing and scraping for the high lights in finishing.
Another style of aquatinting is done by placing a clean plate in an air-tight box where there has been a dust of rosin circulated by means of a bellows attached to the box. The finest of the particles of rosin are allowed to settle on the plate, which is then heated until this dust of rosin sticks to it where it has fallen. The acid is now put to work as before. This gives an even tint something like the other process, the difference being in this cae that the acid bites the plate between the particles of rosin, making a black around a white, whereas in the first process the acid acts through the granulated rosin, producing a black surrounded by a white. An impression of either of these plates, taken in ih.e condition the acid leaves them, would resemble a tint or wash of color on paper.
David Allan engraved his celebrated illustrations of the Gentle Shepherd in this manner. This style of engraving has now gone almost entirely out of use, having been—like engraving in imitations of drawings in chalk or pencil—in a great degree superseded by lithography.
Mezzotint is said to have been invented by Prince Rupert, or by Leivis Siegen, a lieutenant in his service, in or about 
Fig. 2.—The Rocker. the year 1611, and to have been suggested by the rust on a weapon which a soldier was cleaning.
The plate is prepared (before any design is made upon it) by means of an instrument or tool called the "rocker" (see Fig. 2). This "rocker" is rocked to and fro upon the plate in all directions, and the teeth in the sharp, beveled edge of the tool make a small dent in the copper or steel and raise a corresponding "burr." The whole plate is gone over with this instrument about eighty times before it is in a fit condition to be worked upon. When sufficiently prepared it presents a fine, soft-looking, and perfectly even grain, and if in this state a proof is taken from it by the usual process of plate printing the result is the richest possible black.
On this plate, after a tracing has been transferred, the engraver goes to work, with tools called "scrapers" and "burnishers," working from dark to light by removing the dents and burrs, and exactly in proportion as he removes them the tint becomes paler and paler, those parts most smoothed being the lightest and the part the least operated on producing the deepest shadows. As the process is from dark to light, the engraver has to be very cautious not to remove too much of his grain at once, for once he has it too light it would be impossible to restore the color without destroying the surrounding lights. He proceeds from dark to half dark, from half dark to middle tint, from middle tint to half light, and from half light to light. When the work is good the result is soft and harmonious, well adapted to the interpretation of some painters, but not of all.
More than one hundred engravers in mezzotinto employed themselves on the portraits of Sir Joshua Reynolds, and the best of their works are now valued as the classics of the art which is connected with the name of Reynolds, just as line engraving is connected with that of Raphael.
In engraving in "stipple," which was much in vogue in the end of the last century, the drawing and effect are produced by small dots in place of lines (Fig. 3),
These dots follow at first the outlined shades, starting with a double dot where the darker shades are desired. Smaller dots are placed close to these double dots on the side nearest the largest space. Lights are had by using very fine dots, and high lights by leaving them out altogether.
Ryland, Bartolozzi, and Sherwin excelled in this style of engraving. It is well suited for portraits; several of Rasburn's 
Fig. 3.—Stipple. have been capitally engraved in "stipple" by Walker. It involves much more labor than any other kind of work in this line of fine arts, except line engraving, and is now little practiced.
Rouletting is done with a tool very much like those sold on the streets nowadays for cutting glass. A small hardened steel wheel is set in the end of a pencil-like handle (Fig. 4). On the edge of this wheel is cut the pattern desired by the artist—notches, lines, dots, or whatever may be called for by the subject to be treated. This wheel is rolled on the plate, leaving an indentation like the marking on its edge.
This peculiar style of engraving is used, in connection with others, where particular effects are desired, pencil and charcoal lines being imitated in this way, thus securing that beautiful sketchy style better than can be obtained by any of the others. 
Fig. 4.—The Roulette. We now come to consider line engraving, the most important as well as the most difficult of them all, and the only kind that can be used successfully in bank-note work (Fig. 5).
It is so called because the effect is produced by a combination of lines or interrupted lines. The more harmonious these lines are in shape or direction, spacing, and texture, the better will be the effect and the more valuable the work. Because of the requirement of this accurate spacing and harmony of texture mechanical as well as artistic skill is called for in producing a first-class line engraving. Many good artists in other lines fail in this art for want of this mechanical skill.
Line engravings have always ranked the highest in this branch of the fine arts, some people preferring them to water colors or oil paintings.
As stated before, this is the only picture work that can be used successfully in bank-note work, for it is much more difficult to imitate, and consequently gives greater security, being less liable to be counterfeited. This is so also because a line cut with a graver is smooth, sharp, and clean, whereas an etched or bitten line is ragged and rough.
Line engraving is the most expensive, for it takes much more time to produce a picture by this process than by any other. 
Fig. 5.—Line Engraving. Some of the large plates by the late James Smillie, father of the James D. Smillie mentioned earlier in this paper, and who was the best artist of his time in America, cost as high as ten thousand dollars, and took the greater part of two years to complete.
Bank-note Engraving.—For the sake of convenience we will divide bank-note engraving into two classes: 1. Lettering. 2. Picture and scroll work.
Lettering may be described under three heads—large lettering, such as bond titles; small lettering, like that done on coupons, cards, and tickets; and script or writing. Some engravers can do good work in all of these branches of lettering, but in large establishments each man is kept employed at that style in which he excels.
In bonds and stock certificates the titles and script are usually done on the plate from which they are to be printed, but there is a lot of small work, common to jobs of that kind, which is done on what are called "dies" or "bedpieces," and transferred from the rolls to the plates. This will be more fully de scribed later.
In large lettering a drawing of the outline of the letters is made on paper to get the shapes, curves, and spacing correct. A tracing of this outline is then made on gelatin, and, after filling this with vermilion, a thin coating of wax is laid on the plate and a transfer of the gelatin tracing put on the wax. Next the outline is carefully marked through the wax on to the plate; the wax is taken off and the artist is ready to begin his cutting.
Lettering on bank notes, if there is to be more than one note on a plate, is engraved on "dies" or "bedpieces" and transferred to the plate. This insures the exact duplication of the material of each of the notes, and also makes it possible to reproduce and retouch the work at any time.
Picture and Scroll Work.—Picture and scroll work is the most expensive connected with the bank-note business, and is divided into three classes, viz., scroll, portrait, and vignette engraving. It is a very unusual thing to find a man who is a first-class artist in more than one of these branches, and there are none that are even good in all three. This is one of the safeguards of the bank-note business, as no one man can finish a note completely, but must find some one to help him.
The dies and bedpieces mentioned above are pieces of annealed steel—that is, steel that has been softened without decarbonizing—on which work has been engraved that is to be used several times on the same "job," or for a number of different plates. These dies, after "proving," are hardened by heating in cyanide of potassium, which is used in all hardening processes connected with the bank-note business. After these dies are hardened a roll made from very soft steel is rolled over the work under a pressure of from six to twenty tons to the line. This pressure is had by means of a machine called a transfer press.
Fig. 6.—Transfer Press. A, Roll in carrier; B, die or bed piece; C, foot lever; D, rack to fasten lever down; E, side wheel by which bed of press is moved back and forth; F, rack and pinion connecting them; G, G, fulcrum pins of upper and lower levers; H, connecting rod between two levers; I, counter balance.
which, by a combination or compounding of levers, multiplies the pressure exerted by the operator from one hundred to one hundred and fifty times (Fig. 6).
By means of the large wheel on the side of the press, the shaft of which is geared into a rack fastened to the bed of the press, the roll, with this tremendous pressure still on it, is rolled back and forth on the die until the fine grain of the soft steel is forced into every line of the work. This gives the reverse of the die on the roll. Even the finest and faintest scratch of a diamond point can be taken up this way and retransferred to another piece of steel and printed to the paper, so little is lost in the operation.
The roll is now put through the same process of hardening previously used on the die, and we are then prepared to make a great many duplicates of the original. One hundred or more facsimiles of the die can be made in less time than it took to produce the original. For instance, it takes a picture engraver about six weeks to engrave a portrait like that of Martha Washington on the left of the one-dollar United States note, and it can be reproduced in fifteen minutes by means of the transfer press and a roll taken from the original die.
Imagine, if you can, the work it would be to engrave by hand the two hundred postage stamps that are usually put on the plate from which they are printed, or the forty or fifty coupons of a bond. An endless job, you say, and yet that is just what would have to be done if it were not for the transfer press. And not only is it possible to thus readily multiply facsimiles of the original, but the reproductions are exact in every respect and detail, excepting the almost imperceptible loss in the process, which is natural and unavoidable.
Transferers work from a paper model made with prints from the original dies, which are very carefully put together in such a way as will give a very good idea of the effect of the finished work. These models are also submitted to and accepted by the party for whom the work is to be done.
After the plate is transferred it shows hollows around the work, made by the pressure of the roll, which must be brought back to a flat surface again; otherwise a clean proof could not be taken. These hollows are flattened by first carefully marking the outline of the work on the back of the plate, by means of "calipers" made for the purpose, then laying the face of the plate on a polished hardened-steel anvil and hammering around the outline. All scratches, guide lines, and marks that have been used by the transferer are then removed by burnishing the surface, and the plate is ready for the engraver's hands, for there is always some flourishing and finishing to be done before the plate is ready for the printing press.
Plate printing is the opposite of block or woodcut printing in this respect: The line that is to print the color is cut into and below the surface in plate work, and may be so fine that it can not be seen without the aid of a strong magnifier, and yet print perfectly clear and unbroken, while in block the line is left standing and must have some appreciable thickness. For this reason wood engraving can never be as delicate as plate, for it could not be printed. And not only does an impression from plate excel in delicacy but also in force and depth of color.
There never was and never will be a woodcut line having the power of a deep line in a plate, for, in an impression from wood, the print is only a blackened surface of paper, whereas that from plate is a cast with an additional thickness of ink, for the damp paper is forced into the line and brings out the ink upon its embossed surface.
Plate ink is soft and thin as compared with that used for surface prints, and the body of it is ground carbon mixed with oil for black; and colored ink is made from white lead mixed with dry colors and very finely ground in oil. Some inks are much more wearing on the plates than others, green being about the worst in this respect.
Retouching, or "re-entering," as it is called in the trade, is done by re-entering the roll upon the lines of the transferred work and putting the pressure on, as in the original transfer. This sharpens and restores the line, making it print as good as when new.
The very best linen fiber paper is used in printing bank notes, bonds, stock certificates, etc., and it is dampened before printing to make it more pliable, and it also takes the ink better in this condition. After printing the sheets are placed on racks in a drying room heated by steam. When they are thoroughly dry they are found wrinkled and curled, so they are placed between Bristol boards and put under a hydraulic pressure of several hundred tons and kept there for a few hours, then taken out ready for trimming, numbering, and shipping. Each time the impressions are handled they are counted and kept track of, good or bad, so there shall be no possibility of loss or theft.
There are some very delicate machines used in bank-note work, known as ruling machines and cycloidal and geometric lathes. The straight and curved line ruling machine is used in making the background of portraits and vignettes, shade and ruled faces of letters, background of panels, and is capable of ruling three thousand six hundred lines to the inch with great perfection and regularity, but is seldom set as fine as this.
The cycloidal ruling machine is more complicated than the plain line ruler, having from one to four "eccentrics," or "cams," in connection with the forward and back movement of the bed, and is used for producing fine tints to print over other colors and work. The principle of its operation is readily understood. A diamond point is arranged in the machine and given a circular motion by the action of the "cams." Now, while the point is revolving, let a forward movement be given to the plate and the line traced by the point will assume a form like this (Fig. 7), which is called a "cycloidal line," and may be described as that line produced by a point revolving about a moving center. The shape of the curved line depends upon the relative rate of speed of the two motions, the circular one of the point and the forward
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| Fig. 7.—Open Cycloidal Line. | Fig. 8.—Wide Cycloidal Line. | |
one of the plate. If the latter is comparatively slow, the cycloid will take this shape (Fig. 8); if still slower, the curves will cross each other instead of nearly touching. If the motion of the plate is comparatively rapid, the cycloid will take the form of Fig. 9, or one still more open.
By repeating these lines and causing them to overlap each other beautiful lacelike effects can be had, very difficult to imitate by hand (Fig. 10). The patterns can be varied almost endlessly.
Machine engraving of a far more intricate character is produced by the "geometrical lathe," which is one of the most delicate and complex machines ever invented (Fig. 11).
Americans have particularly distinguished themselves in mechanical engraving, and, in fact, it was one of our people—a Mr. Spencer, of Philadelphia who introduced the "bank-note engraving machine" in the early part of this century. This machine, however, was very primitive, as it had but one "cam," and consequently was very limited in its possibilities as compared
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| Fig. 9.—Cycloidal Line. | Fig. 10.—Cycloidal Pattern. | |
with those built in the present day, which have seven cams as well as other attachments not dreamed of by Spencer.
The geometrical lathe of the present day can not be described so as to be perfectly understood, but something of an idea of its working can be gained from the following:
A tool, mechanically sharpened and shaped, made of hardened steel, is used on this machine and is fixed solidly and immovably in a rest, or carrier, over the chuck of the lathe. If the chuck were now revolved the result would be a plain circle cut into the steel plate; or, if the oval slide which is built into the chuck is in operation, the result would be an oval (Fig. 12).
The several cams, when in use, cause the "beds" (of which there are two, laid on rollers) to move back and forth, or to the right and left, as the operator may desire, once for each revolution. Now, suppose one cam was geared to revolve eight times while the chuck is revolving once, we would then have eight
Fig. 11.—Geometrical Lathe. From "Paper and Press," by the kindness of W. M. Patton.
vibrations of the "bed," or eight waves in the line which was before a plain circle; therefore, we would now have an eight-sided figure, or a circle with eight bulges in it, (See inside line of the figure below.) If we now put another cam in motion, geared to revolve twenty-four times to the chuck once and the first cam's eight times, we would have twenty-four waves upon eight waves upon a circle, giving a line like that of the outside in the same figure (Fig. 13).
This has given us one of the many beautiful and perfectly geometrical forms that this wonderful and almost human machine is capable of producing under the management of a skilled artist. Figs. 14 and 15 will show some of the more complicated designs and effects that may be had from one of these lathes. These look to be very complicated, but are, in reality, quite simple: Fig. 14 having but five continuous lines, including the two plain circles
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| Fig. 12.—Circle and Oval Lines. | Fig. 13.—Eight Wave and 8 24 Wave Figures. | |
of the outside, and Fig. 15 has but two; the beautiful effects being produced by the crossing and interlacing of the lines.
Some of the cuttings used for bank notes appear to have thousands of lines, but very few of them have more than twenty, and most have but three or four.
The above diagrams have been engraved for this article by the lathe itself. They have been purposely made much more simple than those used in the bank-note business, in order that the general form may be more readily distinguished. Any one with a
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| Fig. 14.—Lathe Work. | Fig. 15.—Lathe Work. | |
glass and a sharp point may follow the lines which compose these figures.
One peculiarity of lathe-work should be noted. We said, in a former paragraph, that in steel-plate engraving the line cut by the graver prints black. In most of our diagrams, as well as on the notes themselves, the line is white the—interspaces being black. The reverse would be the case if this lathe-work was printed from the plate as it is engraved by the machine. This reversal (making that sunk on the plate which is left raised by the lathe, and vice versa) is effected by a process that is one of the carefully guarded secrets of the trade, and therefore can not be described here. Its effect, however, is evident.
We may suppose, for instance, that a very careful engraver might possibly cut upon a plate a very fair imitation of the lines forming the figure in our last diagram, but these cut lines, remember, would print black and would give an entirely different effect; therefore the black diamonds between the white lines must be cut and the line left standing; and what hand, be it ever so skillful, could cut these black interspaces and leave the white lines in their purity and regularity? Yet this is just what the engraver must do who would reproduce on steel this figure; and, we repeat, this is far less elaborate than those in actual use on bank notes.
The tool which cuts these delicate lines is made of the finest steel; made very hard and very carefully tempered. It passes through each line of the cutting about twenty times, cutting down about one three-thousandth part of an inch each time, then continues going over the line about fifty times more to clean out the burr and polish the work. The machine must, therefore, work with perfect precision, for a deviation of one tenth part of a hair's breadth would destroy the whole cutting.
On account of this required precision, these lathes are made adjustable in every part—that any loss-motion caused by wear may be taken up. They are so sensitive as to be affected by a sudden change of temperature in the room; and if a partially finished line should be entered by the tool after such sudden change, the result would be a defective piece of work.
We may watch one of these machines for hours and each moment discover some new movement. In the hands of a skillful operator (for, after all, the machine itself, to produce the required effects, must be under the direction of human intelligence) it will produce almost any form desired.
There are only three or four first-class operators of these machines in the world, and they are all Americans. Only one of these is able to make a cutting from a pencil sketch and figure out the required combination of wheels, set the lathe, and know it is properly set and adjusted before turning a wheel. The turn of a screw, the substitution of one wheel for another with the variation of a single cog—the shifting of the axis of an eccentric, will produce an entirely new effect; it may give distortion where perfect regularity is demanded; therefore a perfect and long familiarity with the machine is necessary to the successful handling of it.
These machines cost about five thousand dollars, and are built by the inventor, Mr. C. W. Dickinson, Sr.,of Belleville, N. J., who has invented and improved several other kinds of very useful bank-note machines.
It is said the American Bank-note Company, of New York, has a lathe, built by the company some years ago, which took about three years to build and cost more than ten thousand dollars.
The variety of forms that can be produced on one of these lathes is endless; and if Spencer could have had one of these, instead of the crude one he had, and could have started with the opening of this century and cut a new form every day, Sunday included, and every hour of each day up to the present time, he would still have possibilities enough left to fill out the next century.
This machine and its work have been thus minutely described because it is considered a most important security against counterfeiting; not exceeded in value even by the artistic perfection of the vignettes, or portraits, and lettering.
Doubt as to the character of a bank note has often been settled by a microscopic examination of the lathe-work. Even by means of the lathe on which a cutting has been made, it could not be absolutely reproduced; so, of course, it could not be done by hand or by another lathe. Possibly, after reading this article, some one will look upon a bank note as something more than simply cash.
The results of observations taken by Mr. Hallock, of the Smithsonian Institution, at depths extending to 4,462 feet, in a nearly dry well at Wheeling, W. Va., were communicated to the British Association by the Committee on Underground Temperature. When the observations taken in 1891 were concluded, the well was plugged. The plug was withdrawn in July, 1893. and the observations were resumed. The well, which had been dry before, was filled with fresh water to within forty feet of the top. The results of measurements at various depths between 1,586 feet and 3,196 feet were practically identical with those obtained two years previously, when the well was full of air, the greatest certain difference being only one fifth of a degree. The temperatures at 103 feet, 206 feet, and 300 feet were also observed with suitable thermometers, the temperature at 103 feet being 52·53º, which is 1·2º higher than the true temperature of the soil at that depth, as determined by other observations in the immediate neighborhood.
The four-hundredth anniversary of the establishment of the earliest Slavonic printing press in the country was celebrated throughout Montenegro in July, 1893. The press was set up at Obod by the ruling prince in 1493, before either Oxford or Cambridge had a permanent press. Some of the books printed then are still to be seen at the Monastery of Cajnice, just over the Bosnian frontier. On the occasion of the celebration, universities and learned societies of Europe, including the University of Oxford, sent addresses of congratulation.