Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 3, 1802).djvu/164

i44l M A G on which the magnesia %ill remain : lastly, it is to be v.a.shed till it be totally diyested of its saline taste. White magnesia is of consider- iible service for preventing or le- moving many disorders of children, especially of snch as are troubled with a redundance of acid in the lirst passages j for which purpose it is preferable to the calcareous ab- sorbents. But even magnesia is frequently misapplied, and ought never to be given to infants dis- posed to flatulency, or where no symptoms of acidity can be disco- vered j as it is otherwise apt to lodge in the bowels, and produce obstinate costivenessj being in it- ,sclf an inatUve earth, unless com- bined with acids. Hence it is of- ten, and veiy properly, conjoined with rhubarb ; so that children above one year old may take from iive to ten giTiins of the former, and from one to two grains of the latter 3 while adults generally re- quire one or two scruples of mag- nesia, and from five to ten grains of rhubarb for a moderate dose, — See also Heart-burn, MAGNET, or Loadstone, a Icind of ferruginous stone, which in weight and colour resembles iron ere, though it is somewhat harder and more ponderous. It is occa- sionally discovered in iron mines, being sometimes in large masses of difi'erent forms and sizes, that are partly magnetic, and partly metal- lic. Its colour varies according to the country' whence it is obtained j the best magnets, yhich are im- ported from China and Bengal, are of a deep blood-colour; those of Arabia are reddish; those of Mace- donia, blackish ; and such as are found in Germany, Hungaiy, Eng- land, and other j^arts of Europe, have the appearance of unwrought iron. 'Mag The distinguishing properties c^ the magnet are, 1. Its attraction of iron, as well as every matter containing ferruginous particles j and 2. Its inclination to the poles. Hence it is of essential service iit navigation, and is employed irt construfting the mariners' needles, both horizontal and inclinatory.— • As this subject, however, is but distandy connected withour plan, we shall merely state the most sim- ple method of making artificial v^agnets, which possess the virtues of the genuine loadstone, and have been found very useful in extraft- ing particles of iron from the eye, and other delicate parts of the hu- man frame. — Cavallo direfts the scales, hich fall from red-hot iron^ when hammered, to be reduced into a fine powder, and mixed with drying linseed-oil, so as to make a stitf paste; when it may be moulded into any form required. This mixtuie is to be put in a warm place for .some weeks, till it become perfectlydry, and hard: after which it may be rendered jx>werfully mag- netic by the mechanical application of the magnet. But this friiition of the two metals should be performed in a dired horizontal line from north to south ; by v.'hich simple process, if continued for a sufficient length of time, even two flat pieces of iron or steel may be easily imbued with the magnetic fluid, so as to evince, in a considerable degree, the properties of the genuine load- stone, itl^out having been touched by the latter. In order to increase the attrac- tive power of the native magnet, it is frequently armed, that is, cased, capt, and provided with thin iron plates or bars, after its poles have been polished and pro- perly regulated. Thus, it will sup- port a weight 20, 40^ nay lOO times