1. Marbling and spots, from weak nitrate-bath. TOOVELY'S (PATENT) PHOTOLITHOGRA2. Marbling after toning, from the prints overlying each other.

6. Bronzing of deep shadows, negative is too potash, in combination with an organic substance, transparent.

RECOVERY OF SILVER AND GOLD FROM paper, prepared as above, is then exposed to light

judgment and experience of the operator. A sheet of plain, positive photographic paper is now coated on one side with a mixture, consisting of gelatine, softened and dissolved in water, to which a quantity of bichromate of potash and albumen has been added. The paper, evenly covered with this fluid, is dried in the dark, when it will be found possessed of a smooth glassy surface, and a bright yellow color. This surface is still further improved by passing it through the press in contact with a polished plate.

A suitable piece of positive photolithographis paper thus manufactured is now to be exposed to the action of the light under the negative of the map already described. This is accomplished in an ordinary pressure-frame, the time required varying from 10 to 15 seconds, or several minutes, according to the brightness of the weather. The positive thus obtained presents itself to the eye as a brown drawing upon the clear yellow of the sheet.

tone in the negative emploved. The sheet of pre- | pared paper, with the photographic image thus printed, is placed face downwards on a lithographic stone, grained very fine, or polished according to the nature of the image to be reproduced, and previously arranged in a percussion-press (it can be done in a lithographic press, but the result is uncertain). Place several sheets of damped paper upon the stone over the photographic proof, and apply a heavy pressure; the water contained in the damp paper is pressed through the photographic proof, and dissolves the parts of gum remaining at liberty; the dissolved gum attaches itself to the surface of the stone. When the stone has remained a certain length of time in the press, sufficient to allow the small quantity of soluble gum in the dark shadows to attach itself to the surface of the stone remove the pressure, and withdraw the photographic proof carefully from the stone; a negative image is then visible in gum on the stone, with all the gradations of tone. Dry the stone, either spontaneously or by gently warming it; when well dried, cover the whole surface of the stone with greasy ink, which may be applied with a roller or otherwise; the greasy ink is thus brought into contact with all the parts of the stone untouched by gum; the coating of ink is then removed by passing through the lithographic press, by spirits of turpentine or otherwise, and all the gum removed from the surface by washing. The stone is then rolled in with ordinary printing-ink, and the positive image appears in black; it is then printed as every lithographic drawing, but has the great peculiarity of requiring no etch-lation," its object being to effect a change of that ing, the gum having so far penetrated by pressure into the substance of the stone as to allow of a great number of impressions being taken off. Gum Arabic is preferable, but similar substances can be used instead, such as gelatine, dextrine, and mucilaginous solutions.

The exposed photographic copy of the original is covered all over, while dry, with transfer-ink, which is accomplished by running it through the press with its face in contact with a stone which has already received a coating of such ink. After it is separated from the blackened stone it will be found to have brought away with it an evenly distributed film of inky matter, forced by the pressure into intimate contact with the unexposed, as well as the exposed portion of the surface. This operation is known as "blacking" the positive print; that now to be described is called "coagunature upon the albumen contained in the coating of the organic matter. For this purpose moisture and heat are necessary, and both are applied very simply, by letting the blackened photographio copy swim upon the surface of boiling water with its inky side upwards, for it is important not to wet that with hot water. After the lapse of a certain period, determined by the experience of the operator, he proceeds to the next step in the process, that of washing off." For this purpose the print is laid upon a smooth surface, such as plate of glass or porcelain, and friction with a wet sponge, or other suitable material, is applied to the black inky coating, under which the photographic image still exists, and to develop which is now the object in view. The operator soon becomes aware that the moisture which percolated through the paper from the back, has exerted a softened or gelatinizing influence upon the gelatine in the sensitive coating; it has caused it to swell, and to let go its hold upon the ink. But this change does not extend to those parts of the Wherever the plate is protected from the var-coating which were acted on by light; in other nish by the gum it will be attacked by the acid, and an engraving is produced, which is then printed as an ordinary etching on metal plate.

In photozincography proceed as above described, substituting a zinc plate for a lithographic stone.

In photographic engraving on copper, steel or other metal plates, the preliminary operations are the same as those employed for stone or zinc, excepting that a positive image on glass or paper should, in the first instance, be used instead of a negative. When the plate is withdrawn from the press, and the photographic proof detached from it, it should be well dried for the stone. The plate is then covered with a thin coating of varnish, and when dry may be soaked in water to remove the gum, or immediately plunged in a weak solution of acid, and etched in the usual way of etching on steel or copper.

OSBORNE'S (PATENT) PHOTOLITHOGRA-
PHIC PROCESS.

Let us suppose that a map has been compiled and drawn with great care, and that it is desired to multiply copies of this original in the lithographic process. The first step in the process is to obtain a negative; for which purpose the map is placed upright upon a plane-board, and the camera opposite to it at such a distance as to give the desired ratio between original and copy. A negative is now taken on glass coated with collodion in the usual way, observing the greatest care to avoid distortion of all kinds, and to produce a negative of the highest excellence, success in which depends entirely upon the knowledge,

words, to those places which were unprotected by the opacity of the negative; they remain intact, uninfluenced by the solvent or moistening effect of the water. Accordingly the operator finds fac-simile of the original map gradually develop under his hand as he continues the friction. This process is proceeded with until all traces of ink are removed, save those required to form the picture, which must be clear and distinct in all its details Abundance of hot water is then poured over it, so as to remove every particle of soluble matter, and it is then finally dried, which completes its preparation.

A stone to which a fine smooth surface has been imparted, is now slightly warmed, and put in the lithographic press; upon this is placed (inverted) the positive print, after it has been damped by lying between moist paper, and the whole is then passed repeatedly through the press. On examination the paper will now be found to have at

tached itself firmly to the stone, so that some force is required to separate the two. When the former is removed it brings with it its albuminous coating, which gives to it while damp a parchmentlike appearance; but the ink is gone: it has left the paper for the stone, and on the latter we find a reversed drawing of the map, one which, after it has been properly "prepared," will print as well as if it had been drawn by hand.

PRETSCH'S PROCESS OF PHOTO-GALVAN

OGRAPHY.

prepared and exposed to the action of the light. In the course of a short time (all those parts which are dark in the photograph, protecting the plate from change, and all those which are white, allowing the sunlight freely to pass through and the change to take place), we have a combination of bichromate of potash and gelatine in two different states, one soluble and the other insoluble. Consequently, when the plate is then put into water all the parts which remain soluble are dissolved and we have the picture produced not only in dif out, whilst the other parts remain as they were, ferent lights and shades, but also in different Take a plate of glass, and spread on it ordinary depths, the solution being eaten into by the proglue, to which bichromate of potash and a small cess. When the plate is prepared to this point, quantity of nitrate of silver has been added. For there is poured upon it a preparation of guttainstance, take 2 or 3 solutions of glue, into one of percha, which, being kept under pressure for a which put a little nitrate of silver, into another short time, receives the reverse image of the phobichromate of potash, and into another iodide of tographic picture. This is now prepared for the potassium. The silver and the iodide are for the voltaic battery by being simply rubbed over with purpose of producing a little iodide of silver on fine black lead, and it being placed in connection the sensitive film, so as to produce on the picture with the trough, copper is precipitated on the that grain which is necessary for holding the ink plate, which receives an image the reverse of the in the process of printing. Take the photographic mould. Then by the ordinary electrotype process picture obtained by any of the customary pro-another plate may be obtained, from which copies cesses, and place it on the sensitive plate thus may be printed.

ENGRAVING.

THE different modes of engraving are the following:

1. In strokes cut through a thin wax, laid upon the plate, with a point, and these strokes bitten or corroded into the plate with acid. This is called etching.

2. In strokes with the graver alone, unassisted by acid. In this instance, the design is traced with a sharp tool, called a dry point, upon the plate, and the strokes are cut or ploughed upon the copper with an instrument distinguished by the name of a graver.

3. In mezzotinto, which is performed by a dark ground raised uniformly upon the plate with a toothed tool.

4. In aquatinta, the outline is first etched, and afterwards a sort of wash is laid by the acid upon the plate, resembling drawings in Indianink, bistre, etc.

of excelling in quality. In producing a plate upon this principle, cutting with the graver, etching with the point, and biting or corroding with acids, are the ordinary means employed. This combination of chemical and mechanical together with the artistic, is universal in line engraving. Gravers are of various shapes; those most useful, however, are the lozenge and square. With lines laid in and cut up with this tool, it is useful to represent drapery, hair, flesh, in fact all that pertains to human figure, while with lines slightly cut into the metal through an etching ground, bitten with acid and finished with the assistance of the graver, that kind of line and character of manipulation best calculated to represent landscape, architecture, animals, etc., is obtained. As the steel point with which the etching is done is used much in the manner of a pen or lead-pencil, an ease, freedom and disposition of line is secured, which cannot result from the use of the graver alone. The burnisher is also an important tool, as by a skilled use of this instrument much of the delicacy and tenderness which characterizes a well finished line engraving, is obtained. The scraper is principally used to free the lines made by the other tools from the burr, or roughness which accompanies their application. It is intended in this article to treat of engraving on steel. Copper is now seldom used, but the remarks and instructions, except in so far as biting is concerned, are equally applicable to both. Nitrous acid diluted with water is the medium of corroding copper; nitric diluted with acetic, or even with water, is used for steel. The plates, properly prepared, can be obtained of the manufacturers.

Solid Etching-ground

Is composed of burgundy pitch, 3 parts; asphaltun, 3 parts; beeswax, 1 parts. Increase the wax in proportion to the desired softness; when thoroughly melted by heat, pour into hot water and work into balls of convenient size.

Liquid Ground.

Take a ball of etching ground, break it into pieces of convenient size, place them in a bottle, and pour on sulphuric ether. If too thick, add ether; if too thin, take the cork out until it evaporates to proper consistency.

To Lay à Solid Ground.

Put a ball of ground into a piece of silk; make a dabber with a circular piece of pasteboard from 2 to 3 in. in diameter, and a pad of wadding on one surface about 1 inch in thickness, tied in a

piece of kid-skin or good smooth silk, disposed evenly over this on the under side. Clean the surface of the plate thoroughly with whiting or air-slaked lime; attach in hand-vice; heat the plate until hot enough to boil spittle on the back; rub the ground evenly over the surface required, and use the dabber to distribute it smoothly. If the plate has cooled, heat again to former temperature, then turning the ground downwards, with a lighted candle or taper moved slowly back and forth, as near the surface as may be without touching the ground with the wick, smoke it till sufficiently black. Carefully avoid dust during the whole operation.

To lay Liquid Ground.

Clean the surface of the plate, first with turpentine, then a clean rag and whiting; take an ordinary etching dabber, or make a small ball with raw cotton, cover it with a piece of silk velvet, carefully drawn tight to avoid creases, then dip the dabber in the liquid or pour it on the plate and draw and streak it quickly and evenly; the evaporation of the ether leaves a clear, firm ground.

To Transfer the Outline to the Surface. Various plans are used. If the design to be copied be the size to engrave, the outline may be traced with a pencil on a piece of oil-paper laid over it. This tracing may be transferred by laying it upon the ground, and while damp passing it through the printing press with a piece of damp printing paper laid over it. It may also be retraced upon the ground by laying between the tracing and plate a piece of thin paper, coated on the under side with vermilion or black-lead, and going carefully over the outline with a blunt point, or lead-pencil.

A better plan is to use gelatine paper. Trace the outline on this article with a sharp point, cutting into it; scrape off the raised edges from the lines with a smooth scraper; then fill the cuts with vermilion or black-lead; carefully wipe off the superfluous dust; lay in proper position, fix down with wax, and, while slightly damp, pass it through the printing press, or with the gelatine dry burnish over the back sufficiently firm to set off the outline, taking care not to break the ground. The best and most recent mode is to get a daguerreotype of the design, the requisite size; eut cleanly and smoothly with a sharp point into the copper over all the outline; this done, remove all the raised edges with the scraper, and get an impression from the copper. While this is still damp place it on the ground and pass it through the press. If the impression has been taken with red ink, the outline will at once appear; if in black, pass a hair-pencil dipped in vermilion lightly over the ground, which must be first freed from damp, so that the vermilion may adhere only to the oil from the impression.

Etching.

Fix down with wax, strips of wood or leather aboutin. thick upon the margin. The best and most useful point, is a good stub small round file.

Set it true in a tube, such as are used for handles for parasols; grind off the cutting, and smooth on an oil-stone. The point must be sharpened by rolling it between the palms of the hands, keeping the point on the stone; when once set, it can be easily put in order, by holding it in the right hand, and, while causing it to rotate between the thumb and second finger, draw it smoothly down upon a piece of fine emery paper until the point is perfectly round and sharp, extreme sharpness being undesirable. Hold the point nearly perpendicular between the finger and thumb, draw it without pressure, gently over the emery. The examination of a good specimen of the art will give the best idea of the necessary width, style, etc. As a general rule, the more distant parts are etched close, and the space between the lines should increase, as the approach is made forward. Sufficient pressure must be exerted to cut well into the steel, yet not enough to impede an easy motion. Cut with a steady and equal pressure, so that the lines may all present the same color to the eye, as all inequalities show when bitten. Biting Hard Steel.

The etching completed, carefully cover the unetched surface of the plate with stopping-out var nish, composed of asphaltum dissolved in turpentine, or gum resins, or good sealing-wax, dissolved in alcohol. When dry, form a well around the work, of walling wax, composed of beeswax and burgundy pitch, equal parts dissolved together. Make a convenient spout by which to pour off the acid. The best acid for biting the steel in ordinary use is the commercial nitric, 1 part; acetic, 3 parts. For delicate tints, such as skies, distances, etc., this mixture may be diluted at pleasure with water to any extent, down to the sharpness of strong vinegar. Steel is acted upon by acid, with great rapidity as compared with copper; it must therefore be quickly put on, and quickly removed, and luke-warm water poured over the surface; blow dry with the bellows; the operation is much facilitated by heating both the plate and acid. Scrape off small portions of the ground on the lighter parts, to judge thereby of the quality of line, and stop out carefully all that may be considered dark enough. Continue this process until the stronger portions assume sufficient color for the first biting.

Biting Soft Steel.

The use of acids even on hard steel is uncertain and precarious, much more so on soft or partially factory, resort is had to other materials in search decarbonized; on such nitric acid being unsatisof that success denied to the ordinary means. 1. Corrosive sublimate, oz.; alum, oz.; dissolved in a pint of warm water, bites a fair line. Keep sweeping off the sediment deposited during the process, with a hair-pencil or feather.

of commercial nitric acid and the same quantity of
2. Spencer's, or magnetic acid; dissolve in oz.
water, and 1 oz. of fine silver. In the like propor-
tions, of acid and water, dissolve 1 oz. of mercury.
Then mix solution of silver and of mercury, each,
1 part; water, 25 parts; solution of nitric acid,
part.

started; it will, however, lie perfectly inactive un-
This mixture bites very rapidly when once
til some one of the following plans is used. 1. Heat
touch the steel through the acid and ground;
a steel point by rapid friction or fire, and with it
black deposit at once forms; sweep it off with a
feather. 2. With a strip of zinc polished at both
ends, touch with one end the acid, and with the
other, a clear piece of steel. 3. Wet a part of the
surface of the plate with spittle; this is a very

ready means. 4. Dip a point in ccrrosive subli- | theory framed; the result of experiment proved it mate; this pressed into the steel will force action; to have been well founded, and mezzo-tinto, a comor, 5. Put corrosive sublimate on for a moment, pound Italian term, signifying middle-tint, took a pour rapidly off, and as quickly put on the mag-permanent and respected position among the arts. netic acid.

To Set and Use the Graver.

Lay the sides, the angles of which form the belly, on the oil-stone; rub gently, taking care to keep the part flat upon the stone, until the edge is sufficiently sharp; then, with the handle of the graver in the hollow of the hand, and the forefinger on the belly, hold it at an angle of about 30 degrees, and rub the end till a good point is obtained. In cutting, hold the handle of the graver in the hollow of the hand, and the graver, between the forefinger and thumb, the plate lying solid upon the table, turning it as occasion may require. The outlines of figures are usually dotted in with the etching, slightly bitten, and stopped out, and the serious part of figure engraving now commences, by laying in the lines, according to the taste and skill of the workman, lightly at first, and gradually cutting deeper and broader into the darker parts. Sand-bags and oil-rubbers are exploded institutions.

Aquatint Engraving. Etch the outline; bite slightly in the distance and light parts; more strongly those near at home. Clean the plate well to lay the ground, which is thus done: dissolve resin in proof alcohol; for distance, less resin is required. Increase the quantity for the nearest parts. Pour this mixture over the plate, run off the superfluous matter, and in drying it will form a granulation on the surface. This granulation is fine or coarse in proportion to the quantity, more or less, of resin contained in the alcohol. When the resin is in excess no granulation will form. Stop out, bite, and re-bite, as in etching.

MEZZOTINTO ENGRAVING.

So called from the circumstance that the subjects treated by this method in the earliest period after its invention, were such as admitted of a large amount of middle-tint or half-tone in the distribution of the masses of light and dark; it being then believed that such only were suited to this style of art. The process is of the utmost simplicity, and as the best general idea of it may be obtained from the anecdote related of what suggested the invention, it is perhaps advisable to begin by repeating the story, whether founded on fact or not.

So it is already seen that the operation of mezzotinto engraving is exactly the reverse of every other kind, being from dark to light; as in drawing a picture by means of white chalk on black paper, or by taking a panel of light-colored wood, and having charred with fire the whole surface to blackness, scrape this away again in various degrees of completeness in such manner as to present the lights and shadows of a picture.

The contrivance first used for producing the
roughened surface on the copper-plate, termed the
mezzotinto ground, was a wooden roller, in which
were securely fixed multitudes of steel points,
sharp ends outwards. This was rolled over the
plate with moderate pressure, backwards and for-
wards in every direction, until no particle of the
original polished surface remained unpunctured
by a dot. But the difficulty presented itself of
there being no means of sharpening the steel
points when they broke off, or were worn dull by
repeated use. Consequently there was substituted,
in place of the roller, the instrument called the
rocker, or cradle-tool, or more properly the ground-
ng tool, which continues in use to the present
day, notwithstanding its obvious imperfections,
long time, and nothing better has yet been
for it can easily be sharpened when dull, lasts a
thought of.

chisel, two inches wide, cut all over one side with
The grounding tool is made in form like a broad
grooved straight lines parallel to each other, ex-
lengthwise on the tool, so that when the end is
actly equi-distant and of equal depth. These run
sharpened to a bevel, they form a saw-like edge
of teeth. The toothed edge being sharpened to a
curved shape, the tool is held in a nearly upright
position, its teeth resting on the plate, and is
rocked from side to side, advancing forward with
a slightly zigzag motion. The handle, attached
to a shank at the upper end, is firmly grasped,
the wrist being kept stiff. The elbow rests on the
table as a pivot of the motion. Guide-lines are
drawn on the plate with a pencil or charcoal
against a ruler, parallel to each other, and not
quite so wide apart as the breadth of the tool.
The grounding tool is then held in the position
described, not quite upright, but slightly inclined
forwards, the middle of the tool midway between
the lines, and the elbow in place so that an ima-
ginary line between it and the tool is in the same
direction as the pencil guide-lines on the plate.
The rocking motion is then made with moderate
pressure, stopping on each side as nearly on the
guide-line as possible, great care being observed
to avoid digging in the corner of the tool by rock-
ing too wide a line, and also to avoid rocking re-

Prince Rupert, to whom its origin is popularly attributed, is said to have taken the idea from observing a soldier in camp polishing a rusty sword. The rust had been, on some parts of the blade, entirely removed, while on others it remained in all its original roughness, and in some portions the polishing was half done. This acci-peatedly in the same place, thus making a deep dent suggested that a rapid and effective style of engraving might result, if a metal plate were roughened all over its surface by some means, so that it would take secure hold of a coating of plate-printers' ink when applied, and then, being again removed by grinding, or scraping, or burnishing wherever the middle tints and lights of the picture required, would thus retain the printers' ink just in proportion to the degree of such removal. Where the plate was polished bright, the ink would readily wipe clean away, and in printing leave the paper unstained, forming the high lights of the picture, while in the parts where the roughening was left the ink would refuse to wipe away, and thus would print the extreme darks of the picture. Such was the

irremediable cut. Having continued this opera-
tion until all the spaces between the lines have
been rocked through, what is termed one way has
been completed. Precisely the same operation is
repeated with the guide-lines in another direction,
and then in another, and so on until a full black
ground has been produced, which is when every
particle of the original polish has disappeared.
It is well to make a scale to assist in varying the
direction of the ways, such as a half circle of paper
with lines drawn on it radiating to the circum-
ference, like the spokes of a wheel; the straight
edge of the paper being laid against the edge of
the plate, the ruler is laid against one of the lines
as a guide for the direction about to be worked.

The outline of the intended picture is then