EXPLANATION OF SCIENTIFIC TERMS. 



reign remedy in nephritis, or inflamma- 

 tion of the kidneys. It is chiefly im- 

 ported from Mexico. The wood, 'w'im 

 cleared of its bark, is of a dirty yellow 

 colour; but its infusion in cold w'aterhas 

 a sky-blue tinge, when viewed by a false 

 light, and a gold colour by a true one. 

 A small portion of any acid being mixed 

 with the tincture, both these colours dis- 

 appear ; but the sky-Wue may be restored 

 by means of potash. 



LIMIT. See Gloss. I. 



LIQUIDS, and LIQUIDITY.-See Gloss. I. 



LOADSTONE. See Magnet, Native. 



MACHINE (Latin machina, a frame or 

 contrivance). Any complication of arti- 

 ficial bodies acting upon one another by 

 contact, through the medium and motion 

 of which any effect is produced, is a ma- 

 chine. The initial force which puts the 

 machine in motion is called the First 

 or Prime mover. The point at which that 

 force is applied is the Acting point ; and 

 that in which the effect is produced is 

 the Working point : the machine being 

 the medium through which the power is 

 transferred, and by which it is modified 

 so as to answer the intended purpose. 

 When a simple body is the medium be- 

 tween the actiny and the working points, 

 it is an Instrument. 



MAGNETISM " is that peculiar property 

 occasionally possessed by certain bodies 

 (more especially by iron and some of its 

 compounds), whereby, under certain cir- 

 cumstances, they mutually attract or re- 

 pel one another, according to determinate 

 laws." 



MAGNET, NATIVE, or LOADSTONE, 



is an ore of iron, found in the iron mines 

 of Sweden and other places. 



MAGNETS, ARTIFICIAL, are made of 

 small bars of iron or steel, which, when 

 placed at perfect liberty, turn one end to- 

 wards the north, and the other, conse- 

 quently, in a southerly direction. These 

 two points are termed the North and the 

 South Poles of the magnet ; and a line, 

 supposed to connect these points, is its 

 Axis. The tendency to acquire a direc- 

 tion nearly north and south is its Pola- 

 rity. Either pole of the magnet attracts 

 iron. Slight poles formed at irregular 

 points of the bar, and which tend to dis- 

 turb the attraction of the real ones, are 

 termed Consecutive poles. 



MAGNETIC CURVES. For the forms 

 of these curves, and diagrams illustrative 

 of their properties, see Magnetism, pages 

 1922. 



MARINER'S COMPASS, a well-known 

 instrument, consisting of a small mag- 

 netic bar, called a needle, poised on its 

 centre of gravity, so as to be enabled, 

 with the greatest ease, to turn every way 

 in an horizontal direction. After a few 

 vibrating motions, during which it is said 

 to traverse, the needle takes its direction 



nearly north and south, which direction 

 is said to be in the plane of the Magnetic 

 Meridian of the place where the compass 

 happens to be. The true Geographical 

 Meridian is a plane passing through the 

 zenith and the poles of the earth. The 

 angle, which the magnetic meridian is 

 east or west from the geographical, or 

 true north and south, is different in dif- 

 ferent places and at different times ; aiid 

 this is called the Variation of the Com- 

 pass. See Dipping Needle. 



MAGNETIC FLUID is a hypothetical 

 fluid, by which the phenomena of mag- 

 netism have been accounted for. Some 

 have supposed two such fluids, a Boreal 

 or northern, and an Austral or southern. 



MASS (of matter). See Volume. 



MAXIMUM. In a variable quantity or 

 effect, that quantity or effect which is the 

 greatest possible, under the circumstances 

 in which it is placed, is termed a maxi- 

 mum. Thus, in respect to the sails of a 

 windmill, they may be placed at any 

 angle, but there is one angular direction 

 on which the wind will have more power 

 than on any other, and this is, therefore, 

 termed a maximum. There are other 

 cases, in which we seek for a minimum, 

 that is, the least possible. 



MECHANICS is that science which in- 

 vestigates the nature, laws, and effects of 

 motion and moving powers. 



MECHANICAL POWERS are the simple 

 instruments or elements of which every 

 machine, however complicated, must be 

 constructed : they are the Lever, the 

 Wheel and Axle, the Pulley, the Inclined 

 Plane, the Wedge, and the Screw. 



MELTING POINT. That point of the 

 thermometer which indicates the heat at 

 which any particular solid becomes fluid, 

 is termed the melting point of that solid. 



MENISCUS (Greek mene, the moon) a 

 lens which is concave on one side, and 

 convex on the other ; and so called be- 

 cause it resembles the appearance of the 

 new moon. 



MERIDIAN, MAGNETIC. See Mari- 

 ners Compass. 



METALS, annealing of. See Annealing. 



METAPHYSICS. See Physics. 



METRE. A metre is the French standard 

 measure of length, equivalent to 39.371, 

 or very nearly 39|, English inches. The 

 French measures ascend and descend in a 

 decimal progression. Thus, 



English Inches. 

 A Millimetre is ... .03937 



Centimetre 39371 



Decimetre .... 3.93710 



Metre 39.3/1 



Decametre . . . 393-71 

 Ilecatometre . . 3937.1 

 Chiliometre . . 393? 1 

 &c. 



MICA is a mineral of various colours, but 

 usually gray. It is chiefly distributed. 



