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
Cotton-spinning is a term employed to describe in the aggregate all the operations involved in transforming raw cotton into yarn. The word 'spinning' has also a more limited signification, being used to denote the concluding process of the series. The following affords a general notion of the nature and order of the successive operations carried on in the manufacture of cottonyarn:
(1) Mixing, the blending of different varieties of raw cotton, in order to secure economical production, uniform quality and colour, and an even thread in any desired degree.
(2) Cleaning, an operation partly effected in mixing, partly by scutching, the cotton being prepared in the form of a continuous lap or rolled sheet for the next process.
(3) Carding, an operation in which the material is treated in its individual fibres, which are taken from the lap, further cleansed, and laid in a position approximately parallel to each other, forming a thin film, which is afterwards condensed into a sliver - a round, untwisted strand of cotton.
(4) Drawing, the drawing out of several slivers to the dimensions of one, so as to render the new sliver more uniform in thickness, and to place the fibres more perfectly in parallel order.
(5) Stubbing, the further drawing or attenuation of the sliver, and slightly twisting it in order to preserve its cohesion and rounded form.
(6) Intermediate or second stubbing, a repetition of the former operation and further attenuation, not necessary in the production of coarse yarns.
(7) Having, a continuation of the preceding, its principal object being to still further attenuate the sliver, and give it a slight additional twist.
(8) Spinning, which completes the extension and twisting of the yarn. This is accomplished either with the throstle or the mule. By means of the former machine the yarn receives a hard twist, which renders it tough and strong. By means of the latter yarns of less strength are produced, such as warps of light fabrics and wefts of all kind.
Up to the middle of the 18th century the only method of spinning known was that by the hand-wheel, or the still more primitive distaff and spindle. In 1767 a poor weaver of the name of Hargreaves, residing at Stanhill, near Blackburn, in Lancashire, invented a machine for spinningcotton, which he named a spinning-jenny. It consisted at first of eight spindles, turned by a horizontal wheel, but was afterwards greatly extended and improved, so as to have the vertical substituted for the horizontal wheel, and give motion to from fifty to eighty spindles. In 1769 Arkwright, originally a barber's apprentice, took out a patent for spinning by rollers. From the circumstances of the mill erected by Arkwright at Cromford, in Derbyshire, being driven by water-power, his machine received the name of the water-frame, and the thread spun on it that of water-twist. The next important invention in cotton-spinning was that of the mule, introduced by Samuel Crompton, of Bolton, in 1775, and so called from its combining the principle of the spinning-jenny of Hargreaves with the roller-spinning of Arkwright.
Numerous improvements in cotton-spinning have been subsequently introduced up to the present day, but they are all, more or less, modifications of Arkwright's spinning-frame and Crompton's mule-jenny. Among the principal of these may be mentioned the throstle, an extension and simplification of the original spinning-frame, introduced about the year 1810. Research Cotton-Spinning
A drumlin is an irregular, rounded, hog-backed mound of boulderclay, often from a hundred to two hundred feet high and hundreds of yards long. They are abundant in most flat countries over which an ice sheet has passed. Research Drumlin
A face mold is a template or pattern used by carpenters, and the like, to outline the forms which are to be cut out from boards, sheet metal, etc. Research Face Mold
Folio is a sheet of paper folded once to make two leaves of a book or manuscript, and hence the term is given to paper of a large size used for this purpose. Research Folio
Foolscap is a regular paper size of 13.5 by 16.5 inches, so called because it was originally water- marked with a fool's head and cap during the 13th to the 17th centuries. Brewer maintains that the name is an erroneous corruption of the Italian foglio-capo meaning a folio-sized sheet, but concedes that the error must be very ancient as evidenced by the watermark present during the 13th century. Research Foolscap
Ivory carving is the art of carving ivory for ornamental or useful purposes, practised from prehistoric to modern times. The ivory most frequently used is obtained from elephant tusks, but other types of ivory or substitute materials include the tusks, teeth, horns, and bones of the narwhal, walrus, and other animals, as well as vegetableivory and synthetic ivories. The earliest ivory carvings known were made in the Old Stone Age. The inhabitants of Europe in the Perigoridan period more than 20,000 years ago produced great numbers of ivory, bone, and horn carvings, with nude female figures being the most common subject. Representations of animals occur most often in the subsequent Magdalenian period. In Egypt the art of ivory and bone carving was developed in predynastic times, before 3000 BC . Large numbers of carved figures of men and women, as well as carved combs, hairpins, and handles, have been found in Egyptian tombs dating from predynastic and early dynastic periods. Objects found in Egyptian tombs of later date include carved ivory weapon hilts and furniture and caskets inlaid with ivory carvings.
Mesopotamian ivories frequently show strong Egyptian influence. They include a series of tablets carved with figures in low relief, made at the ancient Assyrian capital Nineveh. The Minoans in Crete, and later the ancient Greeks, were noted for their ivory carvings. The Minoans carved small acrobats and snake goddesses.
The Greeks were famous especially in the 5th century BC for their chryselephantine statues, often of heroic size, in which the flesh was represented in carved ivory and the hair and garments in sculptured gold. Among the Romans, in late imperial times, consular diptychs of carved ivory were much in demand. A consular diptych was a two-leafed tablet decorated with portraits and scenes commemorating the inauguration of a consul. It contained a sheet of wax for writing and was given to friends. Ivory carving flourished under the Byzantine Empire, particularly in the 5th and 6th centuries and from the 10th to the 13th century. Christian figures, symbols, and scenes were the subjects most commonly depicted on ivory book covers, icons, boxes, shrines, crosiers, crucifixes, door panels, and thrones. A masterpiece of Byzantine ivory is the Throne of Maximilian. Most Byzantine carvings, however, were in the form of a diptych. In Europe during the reigns of Charlemagne and his successors in the 9th and 10th centuries, elaborately carved ivory book covers, reliquaries, and altarpieces were produced.
Relatively little ivory carving was undertaken in Romanesque Europe, but it reached great heights in the Gothic period. Gothic ivories from the 13th to the 15th century were chiefly religious, as in earlier periods, but were more for private devotions than ecclesiastical use. Popular objects included diptychs with deeply carved figures and elaborate architectural decoration. Especially fine work was produced in Paris. During the 15th and 16th centuries, ivory carving was not popular, but in the baroque and rococo periods in the 17th and 18th centuries it again came into vogue, especially in Germany and the Netherlands. German craftsmen were known for richly ornamented ivories; Flemish craftsmen produced statuettes and other sculpture- inspired ivory carvings. France again became an important ivory- carving centre. The chief centres of the industry were the French cities of Dieppe and Paris, where large numbers of crucifixes and other religious objects were produced.
During the 18th century, however, the demand for ivories diminished. Ivory recovered its popularity in decorative arts in the Art Nouveau style at the end of the 19th century. Old ivory carvings are especially valued by 20th-century collectors of ivory, but very little ivory work is now produced in the western hemisphere. Muslim craftsmen in the Middle East created ivory inlay in intricate arabesque patterns on furniture and other woodwork. In the Far East the best-known ivories are those of India, Japan, and particularly China. Indians carved figures of their gods and ornate caskets, often imitating Italian styles. Japanese netsukes, small carved purse toggles, are often made of ivory. The Chinese have traditionally esteemed ivory and encouraged their artists to work in it. The art still flourishes today; objects created include statuettes, chess pieces, fans, screens, toilet articles, chopsticks, and models of buildings and boats. The Chinese are world famous for their ivory curiosities, particularly the concentric ivory balls carved one inside the other by Cantonese craftsmen. In Inuit, African, and American Indian cultures, carving in ivory, horn, and bone has been practised from the earliest times to the present day. Research Ivory Carving
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Assaying
