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722

MACHINAE.

MACELLUM (<tyo7rcoAia, Athen. i. 9 ; b

,, Kpeo7rcoAe?oj/), a provision-market, frequent­ed by cooks, fishermen, poulterers, confectioners, butchers, and men of similar occupations. (Varro, de Re Rust. iii. 2.17, de Ling. Lett. v. 32. pp. 147, 148. ed. Spengel ; Plaut. Aulul. ii. 8. 3 ; Ter. Eun. ii. 2. 24 ; Hor. Sat. ii. 3. 229, Epist. i. 15. 31 ; Seneca, Epist. 78.) [FonnM.] From ma-cellum, a provision-merchant was called macel-larius (o\l/oirc!>\r)s9 /cpeo7r<&A7]s). (Sueton. Jul. 26. Pespas. 19 ; Varro, de He Rust. iii. 2, 4.) The Athenians called their macellum els tov^qv, just as they called their slave-markets ds to, aj/SpaTrocJa, their wine-market ets rbv oivov, and other markets by the name of the commodities sold in them. (Poll. ix. 47 ; x. 19 ; Harpocr. s. v. Aefyjua.) [J.Y.]

MACHINAE (wxwai), and O'RGANA (upyava). The object of this article is to .give a brief general account of those contrivances for the concentration and application of force, which are known by the names of instruments, mechanical power~s, machines:, engines, and so forth, as they were in use among the Greeks and Romans, espe­cially in the time of Vitruvius, to whose tenth book the reader is referred for the details of the subject.

The general, but loose, definition which Vitru­vius gives of a machine (x. 3. § 1), is a wooden structure, having the. virtue of moving very great weights. A machina differs from an organon, in­asmuch as the former is more complex and produces greater effects of power than the latter: perhaps the distinction may be best expressed by translat­ing the terms respectively machine or engine and instrument. Under the latter class, besides com­mon tools and simple instruments, as the plough for example, Vitruvius appears to include the simple mechanical powers, which, however, when used in combination, as in the crane and other machines, become machinae. Thus Horace uses the word for the machines used to launch vessels (Carm. i. 4. 2), which appears to have been effected by the joint force of ropes and pulleys drawing the ship, and a screw pushing it forwards, aided by rollers ((^aAcryyes) beneath it. The word organon was also used in its modern sense of a musical instru­ment. [See hydraula.]

The Greek writers, whom Vitruvius followed, divided machines into three classes, the (genus) scanscorium or aKpo€ariK6v (respecting which se« Vitruvius and his commentators), the spiritale or TrvevfjLa.TiK.oi' [hydraula], and the traciorium or /SapoDAfcoy (or fieLvavcrov according to the reading of the old editions) for moving heavy weights. The information which he gives us may perhaps, how­ever, be exhibited better under another classifi­cation.

I. Mechanical Engines.

1. The Simple Mechanical Powers were known to the Greek mechanicians from a period earlier than can be assigned, and their theories were com­pletely demonstrated by Archimedes. Vitruvius (x. 3. s. 8) discourses of the two modes of raising heavy weights, by rectilinear (ei^eTa*/) and circular (icvKXtoTfyj/) motion. He explains the action of the lever (ferreus vectis), and its three different eorts, according to the position of the fulcrum , and gome of its applications, as in the

MACHINAE.

steelyard (trutina, statera}, and the oars and rudder-oars of a ship; and alludes to the principle of virtual velocities. The inclined plane is not spoken of by Vitruvius as a machina, but its properties as an aid in the elevation of weights are often referred to by him and other writers ; and in early times it was, doubtless, the sole means by which the great blocks of stone in the upper parts of. buildings could be raised to their places.

Under the head of circular motion, Vitruvius makes a passing allusion to the various forms of wheels and screws, plaustra, rhedae, tympana, rotae, cochleae,, scorpiones, balistae, prela, about which see the respective articles/ It is worth while, also, to notice the methods adopted by Chersiphron and his son Metagenes, the architects of the temple of Artemis at Ephesus, and by later architects, to convey large blocks of marble from the quarries, by supporting them in a cradle between wheels, or enclosing them in a cylindrical frame-work of wood (Vitruv. x. 6. s. 2) ; and also the account which Vitruvius gives of the mode of measuring the distance passed over by a carriage or a ship, by an instrument attached to the wheel of the former, or to a sort of paddle-wheel projecting from the side of the latter (c. 9. s. 14). What he says of the pulley will be more conveniently stated under the next head.

2. Compound Mechanical Poivers, or Machines for raising heavy weights (machinae tractoriae). Of these Vitruvius describes three principal sorts, all of them consisting of a proper erect frame-work (either three beams, or one supported by ropes) ; from which hang pullies, the rope of which is worked either by a number of men, or by a wind­lass (suculd], or by a large drum (tympanum, afjifyi-ptvcris, Trepirpoxto;') moved as a tread-wheel, only from within. He describes the different sort of pullies, according to the number of sheaves (orbi-culi) in each block (trochlea or rechamus}, whence also the machine received special names, such as trispastos, when there were three sheaves, one in the lower block and two in the upper ; and penta-spastos, when there were Jive sheaves, two in the lower block, and three in the upper (x. 2—5).

II. Military Engines. (Vitruv. x. 15—22 ; Vegetius and the other writers de Re Militari; aries ; helepolis ; testudo ; tormentum ; turris, &c.)

III. Theatrical Machines. [theatrum.]

IV. Hydraulic Engines.

1. Conveyance and delivery of water through pipes and channels. [aquaeductus ; emissarium ; fistula ; fons.] It has been shown, under the articles referred to, that the ancients well knew, and that they applied in practice, the hydrostatic law, that water enclosed in a bent pipe rises to the same level in both arms. It also appears, from the work of Frontinus, that they were acquainted with the law of hydraulics, that the quantity of water delivered by an orifice in a given time de­pends on the size of the orifice and on the height of the water in the reservoir ; and also, that it is delivered faster through a short pipe than through a mere orifice of equal diameter.

2. Mactii?ies for raising toater. The ancients did not know enough of the laws of atmospheric pressure to be acquainted with the common sucking pump ; but they had a sort of forcing pump, which is described by Vitruvius (x. 12), who ascribes the invention to Ctesibius. For raising water a small

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