AMA 



AMA 



calico printer, and is employed too, with 

 the greatest advantage, by the fuller and 

 cleaner of cloth. 



ALURNUS, in natural history, a genus 

 of insects of the order Coleoptera. Es- 

 sen, character: antennae filiform, short; 

 feelers four to six, very short : jaw hor- 

 ney, arched. There are three species. 

 A. grossus, an inhabitant of South Ameri- 

 ca and India : A. femoratus, found in In- 

 dia: and A. dentipes, found at the Cape 

 of Good Hope. 



ALYSSO, or ALTSSUM, mad wort, in 

 botany, a genus of the Tetradynamia Es- 

 culosa class of plants: the flower is of 

 the cruciform kind, and consists of four 

 leaves; the fruit is a small roundish cap- 

 sule divided into two cells, in which are 

 contained a number of small roundish 

 seeds. 



The alyssum is arranged in three divi- 

 sions, viz. into A. in which the stem is 

 somewhat shrubby : B. stems herbace- 

 ous : C. silules inflated, or calyx oblong, 

 closed. There are 33 species ; but ac- 

 cording to Martyn only 17. All the spe- 

 cies may be propagated by seed, and most 

 of them by slips and cuttings. In rich 

 ground they seldom live through the win- 

 ter in England; but in dry, poor, rub- 

 bishy soil, or on old walls, they will abide 

 the cold, and last much longer. 



AMALGAM, in the arts. The metals 

 in general unite very readily with one 

 another, and form compounds ; thus pew- 

 ter is a compound of lead and tin, brass 

 is a compound of copper and zinc, &c. 

 These are all called alloys, except when 

 one of the combining metals is mercury ; 

 in that case the compound is called an 

 amalgam : thus mercury and gold form a 

 compound called the amalgam of gold. 



The amalgam of gold is formed very 

 readily, because there is a very strong af- 

 finity between the two metals. If a bit of 

 gold be dipped into mercury, its surface, 

 by combining with mercury, becomes as 

 white as silver. The easiest way of form- 

 ing this amalgam is, to throw small pieces 

 of red hot gold into mercury heated till 

 it begins to smoke. The proportions of 

 the ingredients are not determinable, be- 

 cause they combine in any proportion. 

 This amalgam is of a silvery whiteness. 

 By squeezing it through leather, the ex- 

 cess of mercury may be separated, and a 

 soft white amalgam obtained, which gra- 

 dually becomes solid, and consists of 

 about one part of mercury to two of gold. 

 It melts at a moderate temperature ; and 

 in a heat below redness the mercury eva- 

 porates, and leaves the gold in a state of 



purity. It is much used in gilding. The 

 amalgam is spread upon the metal which 

 is to be gilt ; and then, by the applica- 

 tion of a gentle and equal heat, the mer- 

 cury is driven off, and the gold left adhe- 

 ring to the metallic surface : this surface 

 is then rubbed with a brass wire brush 

 under water, and afterwards burnished. 

 The amalgam of silver is made in the 

 same manner as that of gold, and with 

 equal ease. It forms dentrical crystals, 

 which contain eight parts of mercury and 

 one of silver. It it of a white colour, and 

 is always of a soft consistence. Its spe- 

 cific gravity is greater than the mean of 

 the two metals. Gillert has even re- 

 marked, that when thrown into purefmer- 

 cury, it sinks to the bottom of that liquid. 

 When heated sufficiently, the mercury is 

 volatilized, and the silver remains behind 

 pure. This amalgam is sometimes em- 

 ployed, like that of gold, to cover the sur- 

 faces of the inferior metals with a thin 

 coat of silver. The amalgam of tin and 

 mercury is much used in electricity. See 

 GILDING. 



AMAUANTHUS, in botany, a genus 

 of the Monoecia Pentandria class and or- 

 der, of the Triandria Tryginia of Gmelin's 

 Linnaeus ; its characters are, that those 

 species which have male flowers on the 

 same plants with the females have a ca- 

 lyx, which is a five or three-leaved peri- 

 anthium, upright, coloured, and perma- 

 nent; the leaflets lanceolate and acute , 

 no corolla ; the stamina have five or three 

 capillary filaments, form upright, patu- 

 lous, of the length of the calyx, the an- 

 thers oblong and versatile : of those which 

 have female flowers in the same raceme 

 with the males, the calyx is a perianthi- 

 um the same with the former ; no corol- 

 la? the pistillum has an ovate germ, styles 

 three, short and subulate ; stigmas sim- 

 ple and permanent ; the pericarpium is 

 an ovate capsule, somewhat compressed, 

 as is also the calyx on which it is placed, 

 coloured, and of the same size, three- 

 beaked, one celled, cut open transverse- 

 ly ; the seed is single, globular, com- 

 pressed, and large. There are 22 .-pe- 

 cies, of which we notice A. melancolicus, 

 two-coloured A. with glomerules, axilla- 

 ry peduncled, roundish, and leaves ovate- 

 lanceolate, and coloured. This species 

 varies in the colour of the leaves ; being- 

 in the open air of a dingy purple on their 

 upper surface, and the younger ones 

 green ; in a stove the whole plant is pur- 

 ple-coloured ; but it is easily distinguish- 

 ed in all states by its colour, leaves, and 

 the lateness of its flowering, after all th^ 



