Page:Encyclopædia Britannica, Ninth Edition, v. 16.djvu/40

Rh 30 M E R M E R Meran owes its high reputation as a resort for consumptive and nervous invalids to the purity of its air and its com parative immunity from wind and rain in winter. It stands in 46 41 N. lat., at a height of 1050 feet above the sea, and has a mean annual temperature of about 54 Fahr. Meran enjoys three seasons, being also visited in spring for the whey-cure and in autumn for the grape-cure. The arrangements for the comfort of the visitors are very com plete ; and the environs afford opportunity for numerous pleasant walks and excursions. The favourite promenade of the inhabitants is on a massive dyke, built to protect the town against the encroachments of the Passer. Nearly twenty old castles and chateaus are visible from the bridge over the Passer, the most interesting being Schloss Tyrol, an ancient edifice which has given its name to the entire country. Meran is now frequented by about 6500 patients and 8000 to 9000 passing travellers annually. In 1880 its population, including Obermais and Untermais, amounted to 5334 souls. Meran is probably the representative of the Roman Urbs Majensis, afterwards known as Mairania. It became a town in 1290, and down to 1490 was the capital of the counts and dukes of Tyrol. The town suffered somewhat during the Peasants War in the 16th century, and subsequently from destructive floods. As a health- resort it has been known for about forty years. The whole region in which it lies is singularly rich in historic interest. Authorities. Beda Weber, Meran; Duringsfeld, Aus Meran, 1868; Noe, Der Friihling von Meran; Stampfer, Chronik von Meran, 1867, and Gvschichte der Stadt Meran, 1872 ; Pirclier, Meran als Klimatischer Kurort, 1870 ; Plant, Fiihrer darch Meran, 2d ed., 1879 ; Knoblauch, Meran, 5th ed., 1881. MERCATOR, GERARDUS (Latinized form of Gerhard Kramer) (1512-1594), mathematician and geographer, was born at Rupelmonde in Flanders, May 5, 1512. Hav ing completed his studies at Louvain, he devoted him self to geography, and, after being for some time attached to the household of Charles V., he was appointed cosmo- grapher to the duke of Juliers and Cleves in 1559, taking up his residence at Duisburg, where he died December 2, 1594. One of his earliest cartographical works was a terrestrial globe (1541), followed in 1551 by a celestial globe. In 1552 he published a treatise De usu annuli astronomici (Louvain), and at Cologne in 1569 his Chrono- loffia, hoc est temporum demonstratio. . . ab initio mundi usque ad Annum Domini 1568, ex eclipsibus et observa- tionibus astronomicis, sacris quoque Bibliis, &c. In the same year was published the first map on Mercator s well-known projection, with the parallels and meridians at right angles, for use in navigation. At Cologne, in 1578, appeared his Tabulae geographicx ad mentem Ptolemgei restitutse et emend- atse. The work by which he is chiefly known is his atlas, published in 1594 at Duisburg, in folio, under the title of Atlas, sive Cosmographies meditationes de fabnca mundi. It contains, besides the maps, cosmographical and other dissertations, some of the theological views in which were condemned as heretical ; it was completed by Hondius in 1607. Several of the maps had been previously published separately, the atlas being delayed to allow Ortelius to complete his. Mercator also published in 1592 a Ifar- monia Evangeliorum. MERCURIAL AIR-PUMP. This name is given to two distinct instruments, one of which is founded on statical, the other on hydrodynamical principles. 1. The Statical Pump. The famous spiritualist Sweden- borg was the first to conceive an air-pump in which a mass of mercury, by being made to rise and fall alternately within a vertical vessel, should do the work which in the ordinary instrument is assigned to the piston. He pub lished a description of his pump in 1722; but it is questionable whether his design was ever realized. Of numerous subsequent inventions the only one which, in fact, has survived is the admirably simple and yet efficient instrument first described in 1858, but constructed some FIG. 1. Geisler s time before, by H. Geisler of Bonn, which at once, and justly, met with universal acceptance. The general scheme of Geisler s pump is shown in fig. 1. A and B are pear-shaped glass vessels connected by a long narrow india-rubber tube, which must be sufficiently strong in the body (or strengthened by a linen coating) to stand an outward pressure of 1 to 1-J- atmospheres. A terminates below in a narrow vertical tube c, which is a few inches longer than the height of the barometer, and to the lower end of this tube the india-rubber tube is attached which connects A with B. To- the upper end of A is soldered a glass two- way stop-cock, by turning which the vessel A can either be made to com municate through s and a hole in the hollow cock with the vessel to be ex hausted (I., fig. 2), or through g with the atmosphere (II., fig. 2), or can be shut off from both when the cock holds an intermediate position. The apparatus, after having been carefully cleaned and dried, is charged with pure and dry mer cury, which must next be worked back- ,. , ,. 11, A IT-. Mercurial Air-Pump. wards and forwards between A and B to remove all the air-bells. The air is then driven out of A by lifting B to a sufficient level, turning the cock into position II., and letting the mercury flow into A until it gets to the other side of the stop-cock, which is then placed in the intermediate posi tion. Supposing the vessel to be exhausted to have already been securely connected with b, we now lower the reservoir B so as to re duce the pressure in A sufficiently below the tension in the gas to be sucked in, and, by turning the cock into position I., cause the gas to expand into and al most fill A. The cock is now shut against both a and b, the reservoir lifted, the gas contents of A discharged through , and so on, until, when after an exhaustion mer cury is let into A, the FIG. 2.- -Arrangements of Stop-Cock in Air-Pump. metal strikes against the top without interposition of a gas-bell. In a well-made apparatus the pressure in the exhausted vessel is now reduced to ~$ or -^ of a milli metre, or even less. An absolute vacuum cannot be pro duced on account of the unavoidable air-film between the mercury and the walls of the apparatus. The great advantage of the mercurial over the ordinary air-pump is that it evacuates far more completely than the latter, that it affords direct and unmistakable evidence of the exhaustiveness of its work, and last not least that it enables one to transfer the gas sucked out to another vessel without loss or contamination, so that it can be measured and analysed. On account of this latter feature more especially, the instrument is highly valued as an auxiliary in gasotnetric researches. Without it the researches on which rests our present knowledge of the gases of the blood could not have been carried out. The actual instrument, as constructed for various kinds of work, has of course various complexities of detail omitted in the above description. For these the reader must refer to hand books of practical physiology.