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 university was adjourned, and never completed in Mercator’s lifetime; but he now became cosmographer to the duke and permanently settled on the German soil to which many of his ancestors and relatives had belonged. Soon after this, however, he paid a visit to Charles V. at Brussels, and presented the emperor with a cosmos, a celestial sphere enclosing a terrestrial, together with an explanatory Declaratio: this work marks an era in the observation of longitude by magnetic declination, perfected by Halley. Charles rewarded the author with the title of imperatorii domesticus (Hofrath in the epitaph at Duisburg). In 1554 Mercator published his great map of Europe in six sheets, three or four of which had already been pretty well worked out at Louvain; a copy of this was rediscovered at Breslau in 1889. Herein, though still greatly under Ptolemy’s influence, Mercator begins to emancipate himself; thus Ptolemy’s 62° for the length of the Mediterranean, reduced to 58° in the globe of 1541, he now cuts down to 53°. On the 28th of October 1556 he observed an eclipse at Duisburg; in 1563 he surveyed Lorraine, at the request of Duke Charles, and completed a map of the same (Lotharingiae descriptio); but it is uncertain if this was ever published. In 1564 he engraved William Camden’s map of the British Isles; in 1568 he brought out his Chronologia, hoc est temporum demonstratio ab initio mundi usque ad annum domini 1568, ex eclipsibus et observationibus astronomicis. In the same year was published his memorable planisphere for use in navigation, the first map on “Mercator’s projection,” with the parallels and meridians at right angles (Nova et aucta orbis terrae descriptio ad usum navigantium accommodata). Improvements were introduced in this projection by Edward Wright in 1590; the more general use of it dates from about 1630, and largely came about through Dieppese support. In 1572 Mercator issued a second edition of his map of Europe; in 1578 appeared his Tabulae geographicae ad mentem Ptolemaei restitutae et emendatae; and in 1585 the first part (containing Germany, France and Belgium) of the Atlas, sive cosmographicae meditationes de fabrica mundi, in which he planned to crown his work by uniting in one volume his various detailed maps, so as to form a general description of the globe In 1585 he adapted his Europe to the Atlas; in 1587, with the help of his son Rumold, he added to the same a world-map (Orbis terrarum compendiosa descriptio), followed in 1590 by a second series of detailed maps (Italy, Slavonia, Greece and Candia). The rest of the regional and other plans in this undertaking, mostly begun by Gerard, were finished by Rumold; they include Iceland and the Polar regions, the British Isles (dedicated to Queen Elizabeth), the Scandinavian countries (dedicated to Henr. Ranzovius), Prussia and Livonia, Russia, Lithuania, Transylvania, the Crimea, Asia, Africa and America (in the last Michael Mercator, in Asia and Africa Gerard Mercator the younger, assisted). The designs are accompanied by cosmographical and other dissertations, some of the theological views in which were condemned as heretical (see the Duisburg edition of 1594, folio). In 1592 Mercator published, two years after his first apoplectic stroke, a Harmonia evangeliorum. He died on the 5th of December 1594, and was buried in St Saviour’s church, Duisburg. Besides his famous projection, he did excellent service with Ortelius in helping to free the geography of the 16th century from the tyranny of Ptolemy; his map and instrument work is noteworthy for its delicate precision and admirable execution in detail.

 MERCENARY (Lat. mercenarius, from merces, reward, gain), one who serves or acts solely for motives of personal gain, particularly a soldier who offers himself for service in any army which may hire him. The name is sometimes used as a term of reproach by nations who raise their armies by conscription, of armies raised by voluntary enlistment whose members are paid a more or less living wage.

 MERCER (through Fr. mercier, from popular Lat. mercerius, a dealer, merx, merces, merchandise), a dealer in the more costly textiles, especially in silks and velvets. The word formerly had a wider meaning. Mercery, according to W. Herbert (History of the Twelve Great Livery Companies, 1834), “comprehended all things sold by retail by the ‘little balance’ or small scales (in contradistinction to the things sold by the ‘beam’ or in gross), and included not only toys, together with haberdashery and various other articles connected with dress, but also spices and drugs.” Many of the articles in which they dealt fell later within the sphere of other trades; thus the trade in the smaller articles of dress was taken over by the s (q.v.). The trade in silk seems to have been originally in the hands of the “silkmen and throwsteres.” The Mercers’ Company is the first in precedence of the twelve great livery companies of the city of London, and is also the wealthiest both in trust and corporate property. The first charter was obtained in 1393, but the mercers appear to have been formed into a gild much earlier. Herbert finds the mercers as patrons of a charity a few years after 1172, and one Robert Searle, who was mayor in 1214, was a “mercer.” A further charter was granted in 1424, with the right to use a common seal. The history of the company is closely connected with the name of (q.v.), and later with that of Dean Colet, who chose the company as the manager of St Paul’s School. (See .)

MERCERIZING, the term applied to a process, discovered in 1844 by John Mercer, a Lancashire calico printer, which consists in treating cotton (and to a limited extent other plant fibres) with strong caustic soda or certain other reagents, whereby morphological and chemical changes are brought about in the fibre. Thus, if a piece of bleached calico be immersed in caustic soda of 50° Tw. strength (sp. gr. 1·25), it rapidly changes in appearance, becoming stiff and translucent, but when taken out and well washed in running water it loses these properties and apparently reverts to its original condition. On closer examination, however, the fabric is found to have shrunk considerably both in length and breadth, so as to render the texture quite different in appearance to that of the original calico; it is also considerably stronger, and if dyed in the same bath along with some of the untreated fabric is found to have acquired a greatly increased affinity for colouring matters. This peculiar action is not restricted to caustic soda, similar effects being obtained with sulphuric acid of 105° Tw., nitric acid of 83° Tw., zinc chloride solution of 145° Tw., and other reagents. Mercer assumed that a definite compound, corresponding to the formula C12H20O10.Na2O is formed when the cotton is steeped in caustic soda, and that this is decomposed by subsequent washing with water into a hydrated cellulose C12H20O10.H2O, which would account for the fact that in the air-dried condition mercerized cotton retains about 5% more hygroscopic moisture than ordinary cotton. This view is strengthened by the observation that when cotton is immersed in nitric acid of 83° Tw. it acquires similar properties to cotton treated with caustic soda. If, after immersion in the nitric acid, it is squeezed and then dried (without washing) in a vacuum over burnt lime, it is found to have formed a compound which corresponds, approximately to the formula C6H10O5.HNO3, which is decomposed by water into free nitric acid and a hydrated cellulose.

When viewed under the microscope, mercerized cotton is seen to have undergone considerable morphological changes, inasmuch as the lumen or central cavity is much reduced in size, while the fibre has lost its characteristic band-shaped appearance and becomes rounded.

In Mercer’s time the process, which he himself termed “sodaizing” or “fulling,” never acquired any degree of com-