ALL A L M 
elements, the result is an alloy, or proper considerable portion of land is torn away at 
chemical combination. One of the most once by the violence of the current, and 
striking proofs of actual combination be- joined to a neighbouring estate, it may be 
tween the parts of an alloy, is a remarkable claimed again by the former owner, 
increase of fusibility. This, in almost all ALMAGEST, the name of a celebiated 
cases, is much greater than could be infer- 
red from the mean fusibility of its compo- 
nent parts. Thus, equal parts of tin and 
iron will melt at the same temperature as is 
required for equal parts of tin and copper, 
notwithstanding the great difference be- 
tween 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 
proportion of 3, 8, and 5, will melt in boil- 
ing water, which is a less heat than is neces- 
sary for the liquefaction of bismuth, the most 
fusible of the three. The oxydability of an 
alloy is generally either greater or less than 
that of the unmixed metals. 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 understood 
of another, on account of some similitude 
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 toi rents 
of w ater. The alluvial formations constitute 
the great mass of the earth's surface, ffhey 
have been formed by the gradual action of 
rain or river water upon the other forma- 
tions. They may be divided into two kinds, 
viz. those deposited in the valleys and moun- 
tainous districts, or upon elevated plains, 
which often occur in mountains ; and those 
deposited upon flat land. The first kind 
consists of sand, gravel, &c. which consti- 
tuted 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 neigh- 
bouring mountains. The second kind con- 
sists of loam, clay, sand, turf, and calctuff. 
Here are also earth and brown coal in which 
amber is found, 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 
book composed by Ptolemy ; being a col- 
lection of a great number of the observa- 
tions and problems of the ancients, relating 
to geometry and astronomy; but especially 
the latter. And being the first work of this 
kind which has come down to us, and con- 
taining a catalogue of the fixed stars, with 
their places, beside numerous records and 
observations of eclipses, the motions of the 
planets, &c. it will ever be held dear 
and valuable to the cultivators of astro- 
nomy. See Ptoi.emy. 
In the original Greek it is called trvrrxljie 
the “ great composition” or “ collec- 
tion.” And to the word fxEyifti the Arabian* 
joined the particle “ al,” and thence called 
it “ Almaghesti,” or, as we call it, from 
them, the Almagest. 
ALMAMON, Caliph of Bagdat, a philo- 
sopher and astronomer in the beginning of 
the ninth century, he having ascended the 
throne in the year 814. He was son of 
Harun Al-Rashid, and grandson of Alman- 
sor. Having been educated with great 
care, and with a love for the liberal sciences, 
he applied himself to cultivate and encour- 
age them in his own country. For this 
purpose he requested the Greek emperors 
to supply him with such books of philosophy 
as they had among them; and he collected 
skilful interpreters to translate them into 
the Arabic language. He also encouraged 
his subjects to study them ; frequenting the 
meetings of the learned, and assisting at 
their exercises and deliberations. He formed 
a college at Khorasan, and selected to pre- 
side over it Mesul of Damascus, a famous 
Christian physician. When his father, who 
was still living, remonstrated against the 
appointment, on account of the president’s 
religion, he replied, that he had chosen him, 
not as a teacher of theology, but for the 
instruction of his subjects in science and the 
useful arts, and that his father well knew, 
that the most learned men and skilful artists 
in his dominions were Jews and Christians. 
He caused Ptolemy’s Almagest to be trans- 
lated in 827, by Isaac Ben-honain, and 
Thabet Ben-korah, according to Herbelot, 
but according to others by Sergius, and 
Alhazen, the son of Joseph. In his reign, 
and doubtless by his encouragement, an 
astronomer of Bagdat, named Habash, com- 
posed three sets of astronomical tables. 
