MAC MACHINE ORGANA, defined by Vitruvius, in his 10th book, as contrivances for the concentration and application of force, which are known by the names of instruments, mechanical powers, machines, engines, &c. Machinery, a general term applied to mechanical combinations of parts for creating power, or producing works which may otherwise be, more or less perfectly, made with the hands. The first class of these combinations is usually distinguished by the name of engines; the second, by that of machines. Engines, or machines for creating or accumulating and applying power, are distinguished from each other according to the material employed in the creation of their power, as air-engines, water-engines, gas-engines, steam-engines, electric-engines, &c. Machines employed in the manufacturing arts are named according to their products, as lace-machinery, rope-machinery, papermachines; or to the processes they perform, as spinning-machinery, printing-machinery, sawing-machinery, &c. The materials of which machinery is composed are, wood of various kinds, iron, brass, copper, and other metals, with flexible materials for bands, cords, &c., as wool, caoutchouc, and leather. The several parts of machinery are, frames, plummer-blocks, carriages, bolts and nuts, pins, shafts, wheels, pinions, levers, cranks, springs, screws, pulleys, riggers, bands or belts, and cords, &c., studs, tappets, wedges, rods, cylinders, tubes, pistons, valves, buckets, floats, weights, beams, racks, chains, clutches, winches, &c. The power of engines, as distinguished from machines, depends upon the nature of the material MAC from which their power is gathered. The mere mechanical effect of every piece of machinery is calculable upon its combinations of certain elementary forms, commonly termed the mechanical powers, with deductions from the effect of these for friction between the parts, for rigidity of parts which are theoretically supposed to be perfectly flexible, and for the elasticity of parts which are supposed to be perfectly rigid. The mechanical powers, sometimes described as six in number, viz. the lever, the wheel and axle, the pulley, the inclined plane, the wedge, and the screw, are reducible to two only, viz. the lever and the inclined plane, in each of which the effect produced is just as many times greater than the power employed, as the space through which the power moves is greater than the space through which the effect is continued. Thus, if with a lever a weight be raised ten times greater than the weight or power by which it is raised, this weight or power will have to move through ten times as much space as the height through which the greater weight is raised. Propriety of form in the detail of machinery depends upon two circumstances. The first is, that the parts subject to wear and tear, and influenced by strains, should be capable of motion or adjustment: the second, that every portion should be equally strong, and present to the eye a uniform figure, or one that is consistent with its degree of action: theory, practice, and taste, all must combine to produce such. A great extent of beauty is attainable in all the details, but mathematical reasons cannot be given why a certain arrangement of lines should be preferable to another, provided Truth they are equally strong. Macellum, a market-place for all kinds of provisions Maceria, a rough wall Machicolations, openings formed for the purpose of defence at the top of castles and fortifications, by setting the parapet out on corbels, so as to project beyond the face of the wall Madder carmine, or Field's carmine, is, as its name expresses, prepared from madder. It differs from the rose lakes of madder principally in texture, and in the greater richness, depth, and transparency of its colour, which is of various hues, from rose colour to crimson Madder orange, or Orange lake, is a madder lake of an orange hue, varying from yellow to rose colour and brown Madder purple, Purple rubiate, or Field's purple, is a very rich and deep carmine, prepared from madder. Though not a brilliant purple, its richness, durability, transparency, and superiority of colour, have given it the preference to the purple of gold purple, and to burnt carmine. Madder yellow is a preparation from the madder root. The best is of a bright colour, resembling Indian yellow, but more powerful and transparent, though hardly equal to it in durability of hue; metallic, terrene, and alkaline substances acting on and reddening it as they do gamboge: even alone, it has by time a natural tendency to change in appearance. Maniana, seats in the upper porticoes of the Roman forum, from whence spectators witnessed the combats of gladiators Magnase black is the best of all blacks for drying in oil without addition, or preparation of the oil: it is a colour of vast body and tingeing power Mahogany is a native of the West Indies and the country round the Bay of Honduras. It is said to be of rapid growth, and so large that its trunk often exceeds 40 feet in length and 6 feet in diameter. Spanish mahogany is imported from Cuba, Jamaica, Hispaniola, St. Domingo, and some other of the West India Islands, in logs from about 20 to 26 inches square and 10 feet long. It is close-grained and hard. There is also African mahogany. All the species are used for many purposes, more particularly for superior household furniture. Main links, the links in the parallel motion which connect the pistonrod to the beam of a steam engine Malleable, in metallurgy, capable of being spread by heating or by rolling, a distinguishing character of metals, but more especially of gold. When flattened, it is said to be laminable; when drawn as wire, ductile. Manacaybo is a furniture wood of moderate size, hard, as good as mahogany, and in appearance between that and tulip wood Manchineel, a large tree of the West Indies and South America: it possesses the general character of mahogany, but has a poisonous and unwholesome sap Mandril, the spindle which carries the centre-chuck of a lathe, and communicates motion to the metal to be turned: in small lathes it is driven by a pulley Mandril-frame, the head-stocks or frame bolted to the end of a lathebed, for the purpose of supporting the mandril Mangrove, an aquatic tree, straightgrained, hard, and elastic: much used for ship-building Man-hole, in locomotive engines, an opening in the top of a boiler, used as an entrance when the boiler requires cleaning: it is covered by a strong plate bolted to the boiler plating, so as to be steam-tight Man-hole cover, in locomotive engines, a strong plate of iron, bolted over the man-hole so as to be removeable when required Manipulation, in mining, the manner of digging silver or other metals; a term now generally applied to the means by which materials or effects are produced Manner is that habitude which paint ers have acquired, not only in the management of the pencil, but also in the principal parts of painting, -invention, design, and colouring. It is by the manner in painting that a picture is judged to be by the hand of Titian, Tintoret, Guido, the Caracci, and others. Some masters have had a variety in their manners at different periods of life, and others have so constantly adhered to one manner, that those who have seen even a few of them will immediately know them, and judge of them without any risk of a mistake. The variety observable among artists in their manner and taste arises from the practice of the different schools in which they have received their instruction, or of the artists under whom they have studied. Yet there are many instances of great artists who have divested themselves of that early partiality to a peculiar manner, and have altered it so effectually as to fix on one abundantly more refined and better adapted to their peculiar genius, by which means they have arrived at excellence. Thus, for instance, Raphael proceeded, and acquired a much more elevated manner after he had quitted the school of Perugino. Mannerist, a term applicable to a painter whose pictures have no resemblance to the beautiful varieties of nature, but discover an unpleasing and tasteless sameness Manometer, an instrument intended to measure the rarefaction and condensation of elastic fluids in confined circumstances, whether occasioned by variation of temperature or by actual destruction, or generation of portions of elastic fluids Mansard roof, of French origin, from the name of the inventor; a curb roof Manse, a parsonage-house Mantel-piece, a beam across the opening of a fire-place, serving as a lintel or bressummer to support the masonry above, which is called the chimney-breast Maple wood is considered to be allied to the sycamore or the planetree; its colour is pale: much used for picture frames and Tunbridge ware Marble, a kind of stone found in great masses, and dug out of pits or quarries Marcus, a large iron-headed hammer Market. The market or forum in the cities of antiquity was different from the market in our English towns, where flesh meat, merchandise, &c., are usually sold. The Apostle Paul disputed with philosophers in the market at Athens: this and other evidences prove it to have been also a place of disputation and public resort. Margin or Lock-rail, the flat part of the stile and rail of framed work Marine engine, a steam engine to propel a ship. There are various kinds of them, the beam, directacting, oscillating, &c. (See Tredgold's work.) Marline, a small line used for winding round ropes and cables Marone is of a class of impure colours, composed of black and red, black and purple, or black and russet pigments, or with black and any other denomination of pigments in which red predominates Marone lake is a preparation of madder, of great depth, transparency, and durability of colour: it works well in water, glazes and dries in oil, and is in all respects a good pigment: its hues are easily given with other pigments, but it is not much used Marquetry, chequered or inlaid work; work inlaid with variegation, a sort of veneering, representing flowers, birds, and other figures Masonry. The early Roman archi tecture, both in public and private buildings, was of far more durable materials and of more accurate masonry than such as was executed in the decline of the empire. It began to be uncemented blocks of stone, passed into the reticular work of the republic, thence into the travertine, and descended into the mixture of tufo, and brick, and stucco facing. Masonry. Marble is polished by being first rubbed with grit-stone, afterwards with pumice-stone, and lastly with emery or calcined tin. Marbles, with regard to their contexture and variegation of colour, are almost infinite some are black, some white, and some of a dove colour: the best kind of white marble is called statuary, which, when cut into thin slices, becomes almost transparent, which property the other kinds do not possess. Other species of marble are streaked with clouds and veins. The texture of marble is not altogether understood, even by the best workmen; but they generally know upon sight, whether it will receive a polish or not. Some marbles are easily wrought, some are very hard, other kinds resist the tools altogether. Artificial marble, or Scagliola, is real marble pulverized and mixed with plaster, and is used in columns, basso-relievos, and other ornaments. The chief kind of stone used in London is Portland stone, which comes from the island of Portland, in Dorsetshire; it is used for buildings in general, as strings, windowsills, balusters, steps, copings, &c., but under great weight or pressure it is apt to splinter, or flush at the joints. When it is recently quar ried, it is soft and works easily, but acquires great hardness in course of time. St. Paul's cathedral and Westminster bridge are constructed of Portland stone. Purbeck stone comes from an island of the same name, also in Dorsetshire, and is mostly employed in rough work, as steps and paving. Yorkshire stone is also used where strength and durability are requisites, as in paving and coping. Ryegate stone is used for hearths, slabs, and covings. Mortar is used by masons in cementing their works. (See Bricklaying, Cements, Mortars, &c.) In setting marble or fine work, plaster of Paris is used, and in water-works, tarras is employed. Tarras is a coarse mortar, durable in water, and in most situations. Dutch tarras is made of a soft rockstone, found near Cologne, on the Rhine. It is burnt like lime, and reduced to powder by mills, from thence carried to Holland, whence it has acquired the name of Dutch tarras. It is very dear, on account of the great demand for it in the construction of aquatic works. An artificial tarras is formed of two parts of lime and one of plaster of Paris: another sort consists of one part of lime and two parts of well-sifted coal ashes. Mast carlings, in ship-building, large timbers at the side of the mast rooms that are left deep enough to receive the cross-chocks Mastic, a cement used for the plastering of walls Mastic varnish is easily prepared by digesting in a bottle, during a few hours, in a warm place, one part of dry picked resin with two parts or more of the oil of turpentine Materiatio, according to Vitruvius, the timber-work of a roof Mathematics, a science which teaches to number and measure whatever is capable of it, comprised under lines, numbers, superficies, or solids Matter and Motion. Quantities of matter in all bodies are in the compound ratio of their magnitude and densities; for if the magnitudes are equal, the quantities of matter will be as the densities; and if the densities are equal, the quantities of matter will be as the magnitudes : therefore, the quantities of matter are universally in the compound ratio of both. Mausoleum, a pompous funereal monument, a costly sepulchre Maximum and minimum. The extremes of temperature are no less important to the meteorologist than interesting to the general observer. They are obtained by the self-registering thermometer. The first instrument of this kind was suggested by John Bernouilly. Several forms of thermometers were communicated to the Royal Society by Lord Charles Cavendish. The next in point of time were the contrivances of Fitzgerald and Crighton. Six, Rutherford, Keith, Blackadder, and Dr. Trail, greatly added to the stock of self-registering thermometers. There are two kinds in general use; Mr. Six's, which is placed vertically, and Dr. Rutherford's, which is suspended horizontally. The latter is preferable on land, and, from its simplicity, has to a certain extent superseded the former. Mear, thirty-two yards of ground in a vein of ore Measurement of earth-work. Fig. 1. There are many works and tables published to facilitate the admeasurement of earth-work, which may be reduced in practice to the following geometrical forms, in one or more chains in length, as the case may be. The two chains marked B and c in the section will reduce to the forms in the diagrams that follow. The dotted lines, fig. 1, show the section at the largest end, next to в in the section; and the dotted line, fig. 2. shows the section at the smallest end, next to a in the section. |