MA´CHINAEMA´CHINAE (μηχαναί) and O´RGANA (ὄργανα). 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 powers, 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 (10.1.1), 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. 1.4, 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 (φάλαγγες) 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) scansorium or ἀκροβατικόν, the spiritale or πνευματικόν [HYDRAULA], and the tractorium or βαροῦλκον, according to the most probable reading, for moving heavy weights. Some explanation is needed for the genus scansorium or ἀκροβατικόν, which has been much discussed by commentators. Vitruvius clearly describes the machina which he thus classes. It is a scaffolding formed of upright poles, fixed in the ground with cross planks tied to them, and the “catenationes et erismatum fulturae,” which he mentions afterwards, are no less obviously the ties of sloping supports for these upright poles. It is in fact such a scaffolding as may be seen any day for building purposes, and is the machine below (No. V.) on which Isidore says the workmen stand “propter altitudinem parietum.” It is somewhat of a puzzle, when Vitruvius says that it differs from the other machinae in respect of having audacia rather than ars; but he probably means only this: that a very high scaffolding may cause wonder at its boldness; but there is no scientific principle in it, as in the other classes of machinae, which are mechanical powers. It must be confessed however that his account of its purpose, “ut ad altitudinem sine periculo scandatur ad apparatus spectationem” (unless some such alteration as “ad parietum structionem” is adopted) cannot be explained in a wholly satisfactory manner. If it is for workmen to stand on, it is hard to see why the word spectatio is used, but the only explanations offered by commentators--(1) for seeing theatrical shows, or (2) for viewing the enemy's works within the walls--cannot satisfy us. The theatre had its own tiers of seats: the words sine periculo would be wholly out of place, and moreover it is impossible that he should have so used apparatus when there is nothing in the context to explain its meaning, as is the case in Cic. Fam. 7.1, 1. The same objection must prevent us from adopting the second view, for there is nothing whatever to indicate that Vitruvius is speaking of military affairs. We may be content to say that this class of machina is not what we should call a machine at all, i. e. it had no mechanical power, but was used as we use a scaffolding. The information which Vitruvius gives us may perhaps, however, be exhibited better under another classification. [p. 2.108] 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 (10.3, s. 8) discusses the two modes of raising heavy weights, by rectilinear (εὐθεῖαν) and circular (κυκλωτὴν) motion. He explains the action of the lever (ferreus vectis), and its three different sorts, according to the position of the fulcrum (ὑπομόχλιον), and some of its applications, as in the steelyard [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, redae, tympana, rotae, cocleae, 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 framework of wood (Vitr. 10.6, s. 2; cf. Blümner, Technologie, 3.129 ff.); 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 (100.9, s. 14). What he says of the pulley will be more conveniently stated under the next head. 2. Compound Mechanical Powers, or Machines for raising heavy weights (machinae tractoriae). Of these Vitruvius (10.2-5) describes three principal sorts, all of them consisting of a proper erect framework, from which hang pulleys. He describes the different kinds of pulleys, according to the number of sheaves (orbiculi) in each block (troclea or rechamus), whence also the machine received special names, such as trispastos, when there were three sheaves (as in the explanatory drawing), one in the lower block and two in the upper; and pentaspastos, when there were five sheaves, two in the lower block and three in the upper. The Greek name for the axis (axiculus, Vitruv.) was μάγγανον. In the explanatory drawing by which Blümner illustrates Vitruvius, we see (a) the two upright beams (tigna) supported in place by (h) forestays (antarii funes) and (i) backstays (retinacula), tied at the top by (b) a fibula. From the top hangs (c) a fixed pulley-block (troclea, τροχιλία, Aristoph. Lys. 722): to this the funis ductarius (d） passes from the lower movable block (c), to which again the weight, which is to be raised, is attached by iron grapnels (forfices). In this case the sheaves in each block are double (duplices ordines orbiculorum). The two portions of the
Drawing of a Machina Tractoria. (Blümner,
Techn.iii. fig. 10.)
Commovet atque levi sustollit machina nisu.
” Sometimes, however, the tympanum is of larger size, and is moved as a treadwheel without any capstan by treaders inside it.
|Machina Tractoria, from a relief at Capua. (Blümner.)|