Page:EB1911 - Volume 10.djvu/619

Rh sides of an anticline or syncline are known as the “limbs,” “slopes,” “flanks” or “members” of the fold; in an anticline, the part X, fig. 3, the angle of the bend, is the “crest” or “crown” (Ger. Gewölbebiegung, Fr. charnière anticlinale), the corresponding part of a syncline being the “trough-core” or “base,” Y, fig. 3 (Ger. Muldenbiegung, Fr. charnière synclinale). The portion of an anticline which has been removed by denudation is the “aerial arch,” dotted in fig. 3. The innermost strata in a fold constitute the “core,” arch-core A, fig. 3, or trough-core B, in the same figure. In the majority of folds the bending of the strata has taken place about an “axial plane” (often called the “axis”), which in the examples illustrated in fig. 3 would pass through the points A and B, perpendicularly to the horizontal line CD. In powerfully folded regions the axial planes of the folds are no longer upright; they may be moderately inclined, producing an “inversion,” “inverted fold” or “overfold.” When the inclination of the axial plane is great a “recumbent overfold” is produced (Fr. pli couché, Ger, liegende Falte). In a fold of this kind (fig. 4) we have an “arch limb” (a), a middle limb (b) and a floor or “trough limb” (c). X and Y are the upper and lower bends respectively. One of the important functions of a fold is its direction; this of course depends upon the orientation of the axial plane. The crest-line of an anticline or trough-line of a syncline is rarely horizontal for any great distance; its departure from horizontality is designated the “pitch,” and the fold is said to pitch (or dip) towards the north, &c. Most simple folds—with the exception of very shallow curvatures of wide area,—when considered in their entirety, are seen to be somewhat canoe-shaped in form. There are three variations of the simple fold dependent upon the position of the limbs, (1) the limbs may tend to diverge as they recede from the crest (fig. 3), sometimes styled an “open anticline”; (2) the limbs may be parallel in “closed” folds (commonly known as isoclinal folding); (3) the limbs may make an open angle or widen out towards the crest (fig. 4). This is known as a fan-shaped fold (Fr. pli en éventail, Ger. Fächerfalte); another variant of the same form is the mushroom fold (Fr. pli en champignon). The axial plane is not always extended: it may be so abbreviated that the folding appears to have taken place about a point; anticlines of this type are variously designated “short-anticlines,” “brachyanticlinaux” or “domes”; similarly, there are “short-synclines,” “brachysynclinaux” or “cuvettes.” The dip in cases of this kind has been described as “qua-qua versal” or “periclinal.”

Complex Folding.—Sometimes a simple fold has been itself subjected to further folding repeated more than once, it is then termed a “refolded fold” (Fr. pli replié); fine examples may be observed in the Alps and in other mountain chains. A great regional major fold containing within itself a number of minor “special” or subsidiary folds is described as a “geanticline” (Fr. structure en éventail composé), or as a “geosyncline” (Fr. structure en éventail renversé). Even folds of lesser magnitude may be highly complex in regions of extreme crustal movement, and may contain smaller folds of the first, second, third or higher order (Fr. couches gaufrées [fig. 5]). In its smaller manifestation, this class of folding passes into “crumpling” or “puckering,” where quite a large number of folds may be crowded into a single hand specimen. In “frilling” or “frilled structure” the folds have still smaller amplitude, and in many highly corrugated rocks minute folds are observable with the microscope that do not appear to the unaided eye. When a series of adjacent isoclinal overfolds has passed into a series of thrusts (see ), the so-called “imbricated” structure (Fr. structure imbriquée, Ger. Schuppenstruktur) is generated. Occasionally crust-blocks resembling “graben” and “horsts” are circumscribed by folds instead of faults; when this is so they have been called respectively “infolded graben” or “overfolded horsts.”

The heterogeneous character of great masses of strata has always had a marked influence on the nature of the folding; some beds have yielded much more readily than others, certain beds will be found to be faulted, while those above and below have folded without fracture. In many examples of apparent plasticity it can be shown that this effect has been produced by an infinite number of minute slippings within the rock substance.

The larger rock folds have produced important economic results. For example, in many coal regions the deposits have been conserved in some districts in the synclines or “basins,” while they have been removed by denudation from the uplifted anticlines in others. Near the crest of anticlines is commonly an enriched portion of the ground in mineralized districts; and, in the case of water supply, the tilt of the strata determines the direction of the underground flowage. Again, the most convenient site for oil wells is the crest of an anticline or “dome,” where an impervious stratum imprisons the gas and oil in a subjacent saturated layer under pressure.

For a discussion of the question of the distribution and arrangement of the great folded regions of the earth’s crust, see E. Suess, Das Antlitz der Erde, English translation. The Face of the Earth, vols. i., ii., iii., iv. (Oxford). See also E. de Margerie and A. Heim, Les Dislocations de l’écorce terrestre (Zurich, 1888); A. Rothpletz, Geotektonische Probleme (Stuttgart, 1894).

FOLENGO, TEOFILO (1491–1544), otherwise known as Merlino Coccajo or Cocajo, one of the principal Italian macaronic poets, was born of noble parentage at Cipada near Mantua on the 8th of November 1491, From his infancy he showed great vivacity of mind, and a remarkable cleverness in making verses. At the age of sixteen he entered the monastery of Monte Casino near Brescia, and eighteen months afterwards he became a professed member of the Benedictine order. For a few years his life as a monk seems to have been tolerably regular, and he is said to have produced a considerable quantity of Latin verse, written, not unsuccessfully, in the Virgilian style. About the year 1516 he forsook the monastic life for the society of a well-born young woman named Girolama Dieda, with whom he wandered about the country for several years, often suffering great poverty, having no other means of support than his talent for versification. His first publication was the Merlini Cocaii macaronicon, which relates the adventures of a fictitious hero named Baldus. The coarse buffoonery of this work is often relieved by touches of genuine poetry, as well as by graphic descriptions and acute criticisms of men and manners. Its macaronic style is rendered peculiarly perplexing to the foreigner by the frequent introduction of words and phrases from the Mantuan patois. Though frequently censured for its occasional grossness of idea and expression, it soon attained a wide popularity, and within a very few years passed through several editions. Folengo’s next production was the Orlandino, an Italian poem of eight cantos, written in rhymed octaves. It appeared in 1526, and bore on the title-page the new pseudonym of Limerno Pitocco (Merlin the Beggar) da Mantova. In the same year, wearied with a life of dissipation, Folengo returned to his ecclesiastical obedience; and shortly afterwards wrote his Chaos del tri per uno, in which, partly in prose, partly in verse, sometimes in Latin, sometimes in Italian, and sometimes in macaronic, he gives a veiled account of the vicissitudes of the life he had lived under his various names,