M, In Astronomical Tables, &c, is used for meridional or southern; and sometimes for meridian, or mid-day. In the Roman numeration, it denotes a thousand.

MACHIN (JOHN), a very distinguished mathematician, was some time professor of astronomy at Gresham-college, (to which he was elected May 16, 1713, on the resignation of Dr. Torriano,) and secretary of the Royal Society, died. June 9, 1751. His papers in the Philos. Trans. were, 1. To find the curve which a descending body describes in the shortest time, vol. 30; 2. On a Distempered Skin, vol. 37; 3. A Solution of Kepler's Problem. Besides these, by an approximating series of Dr. Halley's, Mr. Machin computed the circumference of the circle to 100 places of figures. And another ingenious approximating series of his own is given in Mr. Jones's Synopsis Palmariorum Matheseos, 1706, the investigation of which was first given in Dr. Hutton's Mensuration, 1772. Mr. Machin's Laws of the Moon's Motion were printed in Motte's translation of Newton's Principia.

MACHINE, denotes any thing that serves to augment, or to regulate moving powers: or it is any body destined to produce motion, so as to save either time or force. The word, in Greek, signifies an invention, or art: and hence, in strictness, a machine is something that consists more in art and invention, than in the strength and solidity of the materials; for which reason it is that the inventors of machines are called Ingenieurs, or Engineers.

Machines are either simple or compound. The simple machines are the 6 mechanical powers, viz, the lever, pulley, wheel-and-axle, inclined plane, wedge, and screw; which are otherwise called the simple mechanic powers. The balance also is a lever.

These simple machines serve for different purposes, according to their different structures; and it is the business of the skilful mechanist to choose and combine them, in the manner that may be best adapted to produce the desired effect. The lever is a very useful machine for many purposes, its power being readily varied as the occasion may require; when weights are to be raised only a little way, such as stones out of quarries, &c. On the other hand, the wheel-and-axle serves to raise weights from the greatest depth, or to the greatest height. Pulleys, being easily carried, are therefore much employed in ships. The balance is useful for ascertaining an equality of weight. The wedge is very useful for separating the parts

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of bodies; and being impelled by the force of percussion, it is incomparably greater than any of the other powers. The screw is useful for compressing or squeezing bodies together, and also for raising very heavy weights to a small height; its great friction is even of considerable use, to preserve the effect already produced by the machine.

Compound MACHINE, is formed from these simple machines, combined together for different purposes. The number of compound machines is almost infinite; and yet it would seem that the ancients went far beyond the moderns in the powers and effects of them; especially their machines of war and architecture.

Accurate descriptions and drawings of machines would be a very curious and useful work. But to make a collection of this kind as beneficial as possible, it should contain also an analysis of them; pointing out their advantages and disadvantages, with the reasons of the constructions; also the general problems implied in these constructions, with their solutions &c, should be noticed. Though a complete work of this kind be still wanting, yet many curious and useful particulars may be gathered from Strada, Besson, Beroaldus, Augustinus de Ramellis, Bockler, Leupold, Beyer, Limpergh, Van Zyl, Perauit, and others; a short account of whose works may be found in Wolfii Commentatio de Præcipuis Scriptis Mathematicis ; Elem. Mathes. Univ. tom. 5, pa. 84. To these may be added, Belidor's Architecture Hydraulique, Desaguliers's Course of Experimental Philosophy, Emerson's Mechanics, and Dr. Gregory's Mechanics, which contains a description of a great number of the most useful and modern machines. The Royal Academy of Sciences at Paris have also given a collection of machines and inventions approved of by them. This work, published by M. Gallon, consists of 6 vols. in 4to, containing engraved draughts of the machines, with their descriptions annexed.

MACHINE, Architectonical, is an assemblage of pieces of wood so disposed as that, by means of ropes and pulleys, a small number of men may raise great loads, and lay them in their places; such as cranes, &c.—It is hard to conceive what sort of machines the ancients must have used to raise those immense stones found in some of the antique buildings; as some of those still found in the walls of Balbeck in Turkey, the ancient Heliopolis, which are 63 feet long, 12 feet broad, and 12 feet thick, and which must weigh 6 or 7 hundred tons a-piece.

B