Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 3, 1802).djvu/217

Rh skin, affords an efficacious substitute for the Spnnish-fly, as a blister which speedily operates:—it may also be applied in the form of issues.

obtained from the stalks and leaves of the mezereon, a fine vigogne dye; and the stalks, alone, imparted a beautiful gold-brown shade to wool, previously dipped in a diluted solution ot bismuth.—From the ripe berries of this plant, an excellent red lake is prepared by painters.  MICA,, or , a genus of magnesian earths, of which there are two species; viz.

1. The colorata martialis, coloured martial glimmer, of which there are many varieties, distinguished by their brown, black, semi-transparent blue, and green shades: they are found chiefly in Lapland, Sweden, and other northern parts of Europe.

2. The alba, pure or colourless mica, which contains several varieties, that are found in Siberia and Sweden, and are perfectly transparent; whence it has obtained the name of Muscovy-glass.

Both species consist of thin glittering pieces, that are divisible into leaves, or plates; which, when exposed to a moderate heat, become brittle; but, if placed in a strong furnace, they curl or crumple, and are with difficulty reducible into glass. Mica, however, melts easily with borax, by the aid of which it may be converted into glass, with a blow-pipe.

The broad and colourless mica is used in Russia, as a substitute for glass, to which it is preferable; because it resists the shock on the explosion of a cannon.  MICROSCOPE, an optical instrument, consisting of lenses or mirrors, by means of which, small objects appear of a larger size, than they naturally are to the naked eye.

This valuable instrument, though not entirely unknown to the ancients, was re-invented and made public in the early part of the 17th century: it has, since that period, received continual improvements from various ingenious philosophers and artists, among whom the names of, the 's, , and Dr. , deserve to be gratefully recorded.

Microscopes are of two sorts, single and double. The former consist in general of one lens or mirror; but, if a greater number be employed, they only serve to throw additional light upon the object, without farther enlarging its image. Double or compound microscopes are those in which the image of an object is composed of several lenses or mirrors.

The utility of microscopes is very extensive, both to the naturalist and the artist: hence the invention of them must be regarded as one of the greatest efforts of human ingenuity. It is true, they do not contribute in any essential manner to the happiness of mankind; but they serve to unfold the wonders of Nature, and thus insensibly raise the mind to the contemplation of that Great Being, whose works, however minute and apparently insignificant, uniformly evince the highest skill and most perfect symmetry.  MIDWIFERY, or the obstetrical art, a branch of medicine which