It has been abundantly proved that ensilage forms a wholesome and nutritious food for cattle. It can be substituted for root crops with advantage, because it is succulent and digestible; milk resulting from it is good in quality and taste; it can be secured largely irrespective of weather; it carries over grass from the period of great abundance and waste to times when none would otherwise be available; and a larger number of cattle can be supported on a given area by the use of ensilage than is possible by the use of green crops.
Early silos were made of stone or concrete either above or below ground, but it is recognized that air may be sufficiently excluded in a tightly pressed stack, though in this case a few inches of the fodder round the sides is generally useless owing to mildew. In America round erections made of wood and 35 or 40 ft. in depth are most commonly used. The crops suitable for ensilage are the ordinary grasses, clovers, lucerne, vetches, oats, rye and maize, the latter being the most important silage crop in America; various weeds may also be stored in silos with good results, notably spurrey (Spergula arvensis), a most troublesome plant in poor light soils. As a rule the crop should be mown when in full flower, and deposited in the silo on the day of its cutting. Maize is cut a few days before it is ripe and is shredded before being elevated into the silo. Fair, dry weather is not essential; but it is found that when moisture, natural and extraneous, exceeds 75% of the whole, good results are not obtained. The material is spread in uniform layers over the floor of the silo, and closely packed and trodden down. If possible, not more than a foot or two should be added daily, so as to allow the mass to settle down closely, and to heat uniformly throughout. When the silo is filled or the stack built, a layer of straw or some other dry porous substance may be spread over the surface. In the silo the pressure of the material, when chaffed, excludes air from all but the top layer; in the case of the stack extra pressure is applied by means of planks or other weighty objects in order to prevent excessive heating.
The closeness with which the fodder is packed determines the nature of the resulting silage by regulating the chemical changes which occur in the stack. When closely packed, the supply of oxygen is limited; and the attendant acid fermentation brings about the decomposition of the carbohydrates present into acetic, butyric and lactic acids. This product is named “sour silage.” If, on the other hand, the fodder be unchaffed and loosely packed, or the silo be built gradually, oxidation proceeds more rapidly and the temperature rises; if the mass be compressed when the temperature is 140°-160° F., the action ceases and “sweet silage” results. The nitrogenous ingredients of the fodder also suffer change: in making sour silage as much as one-third of the albuminoids may be converted into amino and ammonium compounds; while in making “sweet silage” a less proportion is changed, but they become less digestible. In extreme cases, sour silage acquires a most disagreeable odour. On the other hand it keeps better than sweet silage when removed from the silo.
ENSTATITE, a rock-forming mineral belonging to the group of orthorhombic pyroxenes. It is a magnesium metasilicate, MgSiO3, often with a little iron replacing the magnesium: as the iron increases in amount there is a transition to bronzite (q.v.), and with still more iron to hypersthene (q.v.). Bronzite and hypersthene were known long before enstatite, which was first described by G.A. Kenngott in 1855, and named from ἐνστάτης, “an opponent,” because the mineral is almost infusible before the blowpipe: the material he described consisted of imperfect prismatic crystals, previously thought to be scapolite, from the serpentine of Mount Zdjar near Schönberg in Moravia. Crystals suitable for goniometric measurement were later found in the meteorite which fell at Breitenbach in the Erzgebirge, Bohemia. Large crystals, a foot in length and mostly altered to steatite, were found in 1874 in the apatite veins traversing mica-schist and hornblende-schist at the apatite mine of Kjörrestad, near Brevig in southern Norway. Isolated crystals are of rare occurrence, the mineral being usually found as an essential constituent of igneous rocks; either as irregular masses in plutonic rocks (norite, peridotite, pyroxenite, &c.) and the serpentines which have resulted by their alteration, or as small idiormorphic crystals in volcanic rocks (trachyte, andesite). It is also a common constituent of meteoric stones, forming with olivine the bulk of the material: here it often forms small spherical masses, or chondrules, with an internal radiated structure.
Enstatite and the other orthorhombic pyroxenes are distinguished from those of the monoclinic series by their optical characters, viz. straight extinction, much weaker double refraction and stronger pleochroism: they have prismatic cleavages (with an angle of 88° 16′) as well as planes of parting parallel to the planes of symmetry in the prism-zone. Enstatite is white, greenish or brown in colour; its hardness is 5½, and sp. gr. 3.2-3.3.
(L. J. S.)
ENTABLATURE (Lat. in, and tabula, a tablet), the architectural term for the superstructure carried by the columns in the classic orders (q.v.). It usually consists of three members, the architrave (the supporting member carried from column to column, pier or wall); the frieze (the decorative member); and the cornice (the projecting and protective member). Sometimes the frieze is omitted, as in the entablature of the portico of the caryatides of the Erechtheum. There is every reason to believe that the frieze did not exist in the archaic temple of Diana at Ephesus; and it is not found in the Lycian tombs, which are reproductions in the rock of timber structures based on early Ionian work.