ALL 



ALM 



and two opposite ones smaller than the 

 others ; the corolla consists of four petals, 

 less than the cup, of an orbicular figure, 

 and equal one to another, with large un- 

 gues, of the same length with the smaller 

 leaves of the cup. There are three spe- 

 cies : A. zeylanicus is a tree having 1 the 

 appearance of persea, and a native of Cey- 

 lon. A. cominia vises 30 feet in height, 

 with a stem as thick as a man's thigh, 

 with numerous flowers, to which succeed 

 berries the size of a pin's head, with shell 

 and kernel , grows plentifully in Jamaica. 

 A. ternatus is a native of Cochin China. 



ALLOY, or ALLAT, a proportion of a 

 baser metal mixed with a finer one. Thus 

 all gold coin has an alloy of silver and 

 copper, as silver coin has of copper alone ; 

 the proportion in the former case, for 

 standard gold, being two carats of alloy 

 in a pound troy of gold ; and in the latter, 

 18 penny weights of alloy for a pound 

 troy of silver. 



According as gold or silver has more or 

 less alloy than that mentioned above, it 

 is said to he coarser or finer than the 

 standard. However, it ought to be re- 

 marked, that the coin of different nations 

 varies greatly in this respect ; some using 

 a larger, and others a less proportion of 

 alloy, the original intention of which was 

 to give the coir, a due degree of hardness. 



ALLOY, in a chemical sense, may be de- 

 fined a combination of two or more me- 

 tals into one homogeneous mass, not se- 

 parable from each other by mere heat. 

 The most valuable and useful of these are, 

 brass, type-metal, tutenag, bronze, spe- 

 culum metal, for which see the different 

 articles. If two metals being fused toge- 

 ther produce a mass, whose specific gra- 

 vity is either greater orless than the mean 

 specific gravity of its elements, the result 

 is an alloy, or proper chemical combina- 

 tion. One of the most striking proofs of 

 actual combination between the parts of 

 an alloy is, a remarkable increase of fusi- 

 bility. This, in almost all cases, is much 

 greater than could be inferred from the 

 mean fusibility of its component parts. 

 Thus, equal parts of tin and iron will melt 

 at the same temperature as is required 

 for equal parts of tin and copper, notwith- 

 standing the great difference between the 

 fusing heat of copper and iron, when they 

 are each of them pure. So also an alloy 

 of tin, bismuth, and lead, in the propor- 

 tion of 3, 8, and 5, will melt in boiling 

 water, which is a less heat than is neces- 

 sary for the liquefactien of bismuth, the 

 most fusible of the three. The oxyda- 

 bility of an alloy is generally either great- 



er or less than that of the unmixed me- 

 tals. Tin and lead mixed will, at a low red 

 heat, take fire, and oxydate immediately. 



ALLUSION, in rhetoric, a figure by 

 which something is applied to, or under- 

 stood of another, on account of some si- 

 militude between them. 



ALLUVIAL, by alluvial depositions is 

 meant the soil which has been formed by 

 the destruction of mountains, and the 

 washing down of their particles by tor- 

 rents of water. The alluvial formations 

 constitute the great mass of the earth's 

 surface. They have been formed by the 

 gradual action of rain or river water up- 

 on the other formations. They may be 

 divided into two kinds, viz. those depo- 

 sited in the vallies and mountainous dis- 

 tricts, or upon elevated plains, which of- 

 ten occur in mountains; and those depo- 

 sited upon flat land. The first kind con- 

 sists of sand, gravel, &c. which constitut 

 ed the more solid parts of the neighbour- 

 ing mountains and which remained when 

 the less solid parts have been washed 

 away. They sometimes contain ores, 

 particularly gold and tin, which existed 

 in the neighbouring mountains. The se- 

 cond kind consists of loam, clay, sand, 

 turf, and calctuff. Here are also earth 

 and brown coal, in which amber isfound, 

 wood coal, bituminous wood, and bog-iron 

 ore. The sand contains some metals. 

 The calctuff' contains plants, roots, moss, 

 bones, &c. which it has incrusted. The 

 clay and sand often contain petrified 

 wood, and skeletons of quadrupeds. 



ALLUVION, among civilians, denotes 

 the gradual increase of land along the 

 sea-shore, or on the banks of rivers. This, 

 when slow and imperceptible, is deemed 

 a lawful means of acquisition : but when 

 a considerable portion of land is torn a- 

 way at once by the violence of the cur- 

 rent, and joined to a neighbouring estat3,it 

 may be claimed again by the formerowner. 



ALMAGEST, the name of a celebrated 

 book composed by Ptolemy ; being a col- 

 lection of a great number of the observa- 

 tions and problems of the ancients, relat- 

 ing to geometry and astronomy, but espe- 

 cially the latter ; and being the first work 

 of this kind which has come down to us, 

 and containing a catalogue of the fixed 

 stars, with their places, besides numerous 

 records and observations of eclipses, the 

 motions of the planets, &c. it will ever be 

 held dear and valuable to the cultivators 

 of astronomy. See PTOLEMY. 



In the original Greek it is called 

 <rvvT%i$ fifytw, the " great composi- 

 tion" or " collection." And to the word 



