528 M A II M A R MARATHON was a plain on the north-east coast of Attica, containing four villages Marathon, Probalinthos, Tricorythos, and Oinoe, which formed a tetrapolis. It was divided from the plain of Athens by Mount Pentelicus and the hilly district of Diacria, and was in the early period an autonomous state. After it became incorporated in the Attic state, it retained something of its original distinctive character. The worship of Apollo had its first home in Attica here, and it was carried hence to Athens when the tetrapolis was made part of the Athenian commonwealth. The district was one of the chief seats of the worship of Hercules, and boasted that it was the first place where he had been worshipped as a god. Hence legend localized here several events in the story of the Heraclidse, and especially the self-sacrifice of Macaria, daughter of Hercules. The legend of Theseus was also known in the district ; here the hero slew the Marathonian bull. The plain derived its fame chiefly from the battle in which the Athenians and Plataeans under Miltiades defeated the Persians, 490 B.C. The one hundred and ninety -two Athenians that were slain were buried on the field of battle, contrary to the usual Attic custom, and a mound, which is still called Soro, was erected over them. Another tumulus covered the bodies of the slain Platrcans and slaves, and a special monument was raised to Miltiades. MARBLE is a term applied to any limestone which is sufficiently close in texture to admit of being polished. Many other ornamental stones such as serpentine, alabaster, and even granite are sometimes loosely desig nated as marbles, but by accurate writers the term is invariably restricted to those crystalline and compact varieties of carbonate of lime which, when polished, are applicable to purposes of decoration. The crystalline structure is typically shown in statuary marble. A fractured surface of this stone displays a multitude of sparkling facets, which are the rhombohedral cleavage- planes of the component grains. On placing a thin section of Carrara marble under the microscope, it is seen that each grain is an imperfect crystal, or crystalloid, of calc- spar, having an irregular boundary, and being itself made up of a number of crystalline plates twinned together (see fig. 5, article GEOLOGY, vol. x, p. 231). It is said that a somewhat similar polysynthetic structure may be artificially induced in calc-spar by means of pressure. As marble appears to be, in many cases, a metamorphic rock, it is probable that pressure and heat have been the principal natural agents concerned in the alteration of compact into crystalline limestones. It was shown many years ago by Sir James Hall that even an earthy limestone, like chalk, when strongly heated in a closed vessel, might assume a saccharoidal texture ; and it is a fact familiar to the field-geologist that a crystalline structure is often locally developed in limestone where it happens to have been invaded by an eruptive rock. Prof. Geikie proposes to distinguish this kind of metamorphism by the term mar- marosis (Text- Book of Geoloyy, 1882). Among statuary marbles the first place may be assigned to the famous Pentelic marble, the material in which Phidias, Praxiteles, and other Greek sculptors executed their principal works. The characteristics of this stone are well seen in the Elgin marbles, which were removed from the Parthenon at Athens, and are now in the British Museum. The marble was derived from the quarries of Mount Pentelicus in Attica. The neighbouring mountain of Hymettus likewise yielded marbles, but these were neither so pure in colour nor so fine in texture as those of Pentelicus. Parian marble, another stone much used by Greek sculptors and architects, was quarried in the isle of Paros, chiefly at Mount Marpessa. It is called by ancient writers lychnites, in allusion to the fact that the quarries were worked by the light of lamps. The Venus de Medici is a notable example of work in this material. Carrara marble is better known than any of the Greek marbles, inasmuch as it constitutes the stone invariably employed by the best sculptors of the present day. This marble occurs abundantly in the Apuan Alps, an offshoot of the Apennines, and is largely worked in the neighbourhood of Carrara, Massa, and Serravezza. Stone from this district was employed in Rome for architectural purposes in th& time of Augustus, but the finer varieties, adapted to the needs of the sculptor, were not discovered until some time later. It is in Carrara marble that the finest works of. Michelangelo and of Canova are executed. The purest varieties of this stone are of snow-white colour and of lino saccharoidal texture. Silica is disseminated through some of the marble, becoming a source of annoyance to the workman; while occasionally it separates as beautifully pellucid crystals of quartz known as Carrara diamonds.. The geological age of the marbles of the Apuan Alps has been a subject of much dispute, some geologists regarding them as metamorphosed Triassic or even Liassic rocks, while others are disposed to refer them to the Carboni ferous system. Much of the common marble is of a bluish colour, and therefore unfit for statuary purposes ; when streaked with blue and grey veins, the stone is known as bardiglio. Curiously enough, the common white marble of Tuscany comes to England as Sicilian marble a name probably due to its having been formerly re-shipped from some port in Sicily. Although crystalline marbles fit for statuary work arc- not found to any extent in Great Britain, the limestones of the Palaeozoic formations yet yield a great variety of marbles well suited for architectural purposes. The Devonian rocks of South Devon are rich in handsome marbles, presenting great diversity of tint and pattern. Plymouth, Torquay, Ipplepen, Babbacombe, and Chudleigh may be named as the principal localities. Many of these limestones owe their beauty to the fossil corals which they contain, and are hence known as madrepore marbles. Of far greater importance than the marbles of the Devonian system are those of Carboniferous age. It is from the Carboniferous or Mountain Limestone that British marbles are mainly derived. Marbles of this age are worked in Derbyshire and Yorkshire, in the neighbour hood of Bristol, in North Wales, in the Isle of Man, and in various parts of Ireland. One of the most beautiful of these stones is the encrinital marble, a material which owes its peculiarities to the presence of numerous encrinites, or stone-lilies. These fossils, when cut in various directions, give a characteristic pattern to the stone. The joints of the stems and arms are known from their shape as " wheel-stones," and the rock itself is sometimes called entrochal marble. The most beautiful varieties are those in which the calcareous fossils appear as white markings on a ground of grey limestone. On the Continent a black marble with small sections of crinoid stems is known as petit granit, while in Derbyshire a similar rock, crowded with fragments of minute encrinites, is termed bird s-eye marble. Perhaps the most generally useful marbles yielded by the Carboniferous system are the black varieties, which are largely employed for chimney pieces, vases, and other ornamental objects. The colour of most black limestone is due to the presence of bituminous matter, whence the mineralogical name anthraconite. Such limestone com monly emits a fetid odour when struck ; and the colour, being of organic origin, is discharged on calcination. Black marbles, more or less dense in colour, are quarried in various parts of Ireland, especially at Kilkenny and near
Galway ; but the finest kind is obtained from near Ashford