accumulations of coarse volcanic ejectamenta such as frequently occur near extinct or active volcanoes. Agglomerates in the geological sense, with which this article is concerned, consist typically of blocks of various igneous rocks, mixed often with more or less material of rudimentary origin and embedded in a finer-grained matrix, similar in nature to the coarser fragments. As distinguished from ordinary ash beds or tuffs, they are essentially coarser, less frequently well-bedded; they are less persistent and tend to occur locally, but may attain a very great thickness. Showers of fine ash may be distributed over a wide area of country and will form thin layers of great extent. Coarser accumulations gather only near the actual foci of eruption (craters, fissures, &c.). When the activity of a volcanic vent comes to an end, the orifice is often choked by masses of débris, which will in time become compacted into firm agglomerates. Hence rocks of this type very commonly mark the sites of necks, the remains of once-active volcanic craters. In this connexion they are of especial interest to geologists, as it is always important to be able to locate the exact points at which volcanic products, such as lavas and ash-beds, were emitted.
The blocks in agglomerates vary greatly in size. Some are thirty or forty feet in diameter, and weigh many tons; these are usually pieces of the strata through which the volcano has forced an outlet. They are never far from the crater; most of them, in fact, lie within its boundaries, and cases are known in which enormous masses of this kind (half an acre in area) have been found in such situations. They are masses which have been dislodged, by fissures and landslides, from the crater’s walls and have tumbled into the cavity. Pieces of sandstone, limestone and shale occur in the agglomerates mixed with volcanic materials, and very often have been baked and partly recrystallized by contact with the hot igneous rocks and the gases discharged by the volcano. At Vesuvius such blocks of altered limestone are rich in new minerals and are well known to collectors.
Agglomerates also are usually full of volcanic bombs. These are spongy globular masses of lava which have been shot from the crater at a time when liquid molten lava was exposed in it, and was frequently shattered by the sudden outbursts of steam. These bombs were more or less viscous at the moment of ejection and by rotation in the air acquired their spheroidal form. They are commonly one or two feet in diameter, but specimens as large as nine or twelve feet have been observed. There is less variety in their composition at any volcanic centre than in the case of the foreign blocks above described. They correspond in nature to the lava which at the time fills the crater of the volcano, and as this varies only very slowly the bombs belong mostly to only a few kinds of rock and are similar in composition to the lava flows.
Crystalline masses of a different kind occur in some numbers in certain agglomerates. They consist of volcanic minerals very much the same as those formed in the lavas, but exhibiting certain peculiarities which indicate that they have formed slowly under pressure at considerable depths. Hence they bear a resemblance to plutonic igneous rocks, but are more correctly to be regarded as agglomerations of crystals formed within the liquid lava as it slowly rose towards the surface, and at a subsequent period cast out by violent steam explosions. The sanidinites of the Eifel belong to this group. At Vesuvius, Ascension, St Vincent and many other volcanoes, they form a not inconsiderable part of the coarser ash-beds. Their commonest minerals are olivine, anorthite, hornblende, augite, biotite and leucite.
Agglomerates occur wherever volcanoes are known. In many parts of Britain they attain a great development either in beds alternating with lavas or as the material occupying necks. In the latter case they are often penetrated by dikes. They also show a steep, angular, funnel-shaped dip (e.g. Arthur’s Seat, Edinburgh), and may contain thin layers of clay or ashy sand-stone, which gathered in the crater during intervals of repose. (J. S. F.)
AGGLUTINATION (Lat. ad, and gluten, glutinare, literally to fasten together with glue), a term used technically in philology for the method of word-formation by which two significant words or roots are joined together in a single word to express a combination of the two meanings each of which retains its force. This juxtaposition or conjoining of roots is characteristic of languages such as the Turkish and Japanese, which are therefore known as agglutinative, as opposed to others, known generically as inflexional, in which differences of termination or combinations in which all separate identity disappears are predominant.
The term was also formerly used by associationist philosophers for those mental associations which were regarded as peculiarly close. Combination in its simplest form has been called Agglutination by W. Wundt.
AGGRAVATION (from Lat. ad, increasing, and gravis, heavy), the making anything graver or more serious, especially of offences; also used as synonymous with “irritation.” In the canon law “aggravation” was a form of ecclesiastical censure, threatening excommunication after three disregarded admonitions.
AGGREGATION (from the Lat. ad, to, gregare, to collect together), in physics, a collective term for the forms or states in which matter exists. Three primary “states of aggregation” are recognized—gaseous, liquid and solid. Generally, if a solid be heated to a certain temperature, it melts or fuses, assuming the liquid condition (see Fusion); if the heating be continued the liquid boils and becomes a vapour (see Vaporization.) On the other hand, if a gas be sufficiently cooled and compressed, it liquefies; this transition is treated theoretically in the article Condensation of Gases, and experimentally in the article Liquid Gases.
AGGTELEK, a village of Hungary, in the county of Gömör, situated to the south of Rozsnyó, on the road from Budapest to Dobsina. Pop. (1900) 557. In the neighbourhood is the celebrated Aggtelek or Baradla cavern, one of the largest and most remarkable stalactite grottos in Europe. It has a length, together with its ramifications, of over 5 miles, and is formed of two caverns—one known for several centuries, and another discovered by the naturalist Adolf Schmidl in 1856. Two entrances give access to the grotto, an old one extremely narrow, and a new one, made in 1890, through which the exploration of the cavern can be made in about 8 hours, half the time it took before. The cavern is composed of a labyrinth of passages and large and small halls, and is traversed by a stream. In these caverns there are numerous stalactite structures, which, from their curious and fantastic shapes, have received such names as the Image of the Virgin, the Mosaic Altar, &c. The principal parts are the Paradies with the finest stalactites, the Astronomical Tower and the Beinhaus. Rats, frogs and bats form actually the only animal life in the caves, but a great number of antediluvian animal bones have been found here, as well as human bones and numerous remains of prehistoric human settlements.
AGINCOURT (Azincourt), a village of northern France in the department of Pas de Calais, 14 m. N.W. of St Pol by road, famous on account of the victory, on the 25th of October 1415, of Henry V. of England over the French. The battle was fought in the defile formed by the wood of Agincourt and that of Tramecourt, at the northern exit of which the army under d’Albret, constable of France, had placed itself so as to bar the way to Calais against the English forces which had been campaigning on the Somme. The night of the 24th of October was spent by the two armies on the ground, and the English had but little shelter from the heavy rain which fell. Early on the 25th, St Crispin’s day, Henry arrayed his little army (about 1000 men-at-arms, 6000 archers, and a few thousands of other foot). It is probable that the usual three “battles” were drawn up in line, each with its archers on the flanks and the dismounted men-at-arms in the centre; the archers being thrown forward in wedge-shaped salients, almost exactly as at Crécy (q.v.). The French, on the other hand, were drawn up in three lines, each line formed in deep masses. They were at least four times more numerous than the English, but restricted by the nature of the ground to the same
