Assaying is the estimation of the amount of pure metal, and especially of the precious metals, in an ore or alloy. In the case of silver the assay is either by the dry or by the wet process. The dry process is called eupellation from the use of a small and very porous cup, called a cupel, which is usually made of well-burned and finely-ground bone-ash or of magnesia. The cupel, being thoroughly dried, is placed in a fire-clay oven about the size of a drain-tile, with a flat sole and arched roof, and with slits at the sides to admit air. This oven, called a muffle, is set in a furnace, and when it is at a red heat the assay, consisting of a small weighed portion of the alloy wrapped in sheet-lead, is laid upon the cupel. The heat causes the lead to volatilize or combine with the other metals, and to sink with them into the cupel, leaving a bright globule of pure metallic silver, which gives the amount of silver in the alloy operated on. In the wet process the alloy is dissolved in nitric acid, and to the solution are added measured quantities of a solution of common salt of known strength, which precipitates chloride of silver. The operation is concluded when no further precipitate is obtained on the addition of the salt solution, and the quantity of silver is calculated from the amount of salt solution used.
An alloy of gold is first cupelled with lead as above, with the addition of three parts of silver for every one of gold. After the cupellation is finished the alloy of gold and silver is beaten and rolled out into a thin plate, which is curled up by the fingers into a little spiral or cornet. This is put into a flask with nitric acid, which dissolves away the silver and leaves the cornet dark and brittle. After washing with water the cornet is boiled with stronger nitric acid to remove the last traces of silver, well washed, and then allowed to drop into a small crucible, in which it is heated, and then it is weighed. The assay of gold, therefore, consists of two parts: cupellation, by which inferior metals (except silver) are removed; and quartation, by which the added silver and any silver originally present are got rid of. The quantity of silver added has to be regulated to about three times that of the gold. If it be more the cornet breaks up, if it be less the gold protects small quantities of the silver from the action of the acid. Where, as in some gold manufactured articles, these methods of assay cannot be applied, a streak is drawn With the article upon a touchstone consisting of coarse-grained Lydian quartz saturated with bituminous matter, or of black basalt. The practised assayer will detect approximately the richness of the gold from the colour of the streak, which may be further subjected to an acid test. The Goldsmith's Company of London is the statutory assay-master of all England. Research Assaying
A blanket bog is a very acidpeatbog, low in nutrients and extending widely over a flat terrain. They are found in cold wet climates. Research Blanket Bog
A coulisse is one of the side scenes of the stage in a theatre, or the space included between the side scenes. Properly the term applies to one of the grooved pieces of wood, etc, in which a flat scene moves. Research Coulisse
Drawing is the art of representing upon a flat surface the forms of objects, and their positions and relations to each other. The idea of nearness or distance is given by the aid of perspective, foreshortening, and gradation. The term drawing, in its strict sense, is only applicable to the representing of the forms of objects in outline, with the shading necessary to develop roundness or modelling. In art, however, the term has a wider significance. Highly-finished painting's in water-colour are called drawings, as are also sketches or studies in oils.
Drawing, in its restricted sense, may be divided into these kinds: (1) pen drawing; (2) chalk drawing, which may include lead-pencil drawing; (3) crayon drawing; (4) drawing shaded with the brush or hair-pencil; (5) architectural or mechanical drawing (technical drawing).
Pen drawings are often confined to pure outlines; an appearance of relief or projection being given by thickening or doubling the lines on the shadow side. Finished pen drawings have all the shading produced by combinations of lines. Chalk drawings (including lead-pencil drawings) are most suited for beginners, as errors can be easily corrected. Black, red, and white chalks are used. When the chalk is powdered and rubbed in with a stump, large masses and broad effects can be produced with much rapidity. A combination of hatching and stumping is generally preferable to adhering exclusively to either mode. Crayon drawings are those in which the true colours of the objects represented are more or less completely wrought out with different coloured crayons. Drawings shaded with the brush are outlined with the pencil or pen, the shading being laid on or washed in with the brush in tints of Indian ink, sepia, or colour. Architectural and mechanical drawings are those in which the proportions of a building, machine, etc, are accurately set out for the guidance of the constructor: objects are in general delineated by geometric or orthographic projection.
The great schools of painting differ from one another as much in their drawing as in their painting. In Italy the Roman school, through Raphael's fine sense for the beautiful and expressive in form, and through his study of the antique, became the true teacher of beautiful drawing. The Florentine school tried to surpass the Roman precisely in this particular, but it lost by exaggeration what it had gained by learning and a close study of anatomy. In the Lombard school a tender style of drawing is seen through harmonious colouring, and, in the Venetian school the drawing is often veiled in the richness of the colour. The Dutch school excels in a careful and minute style of naturalistic drawing, combined with great excellence in colouring. The French school in the time of Poussin was very accurate in its drawing; at a later period its style betrayed a great amount of mannerism. David introduced again a purer taste in drawing and a close study of the antique, and these are qualities which distinguish his school (the so-called classical school) from the romantic and eclectic schools of a later period. The drawing of the British school is naturalistic rather than academic. During the 19th century it improved greatly in accuracy and expressiveness. Research Drawing
The knout was a Russian instrument of punishment. It consisted of a handle about 60 cm long, to which was fastened a flat leatherthong about twice the length of the handle, terminating with a large copper or brass ring; to this ring was affixed a strip of hide about five centimetres broad at the ring, and terminating at the end of 60 cm in a point. This was soaked in milk and dried in the sun to make it harder, and should it fall, in striking, the culprit on the edge, it would cut like a penknife. The culprit was bound erect to two stakes to receive the specified number of lashes on the back, and the tail of the knout was changed at every sixth stroke. Punishment by the knout often resulted in the death of the victim. It was abolished by Tsar Nicholas I. Research Knout
A trencher is a flat slab of wood upon which bread, meat or other food is cut. Originally trenchers were square, but afterwards round trenchers were introduced. Except for use as a bread board they fell into disuse when earthenware became generally available. In the 1920's the students at Winchester College still ate from square trenchers. Research Trencher
In building, a trowel is a flat bladed tool with a short handle used for spreading mortar. A gardener's trowel is a scoop shaped tool with a short handle. Research Trowel
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Abbreviations
Research Assaying
