CLA 
cistern of muddy water, and marl is also 
Bsed with advantage in clarifying vinous 
liquors. 
CLARINET, in music, a wind instru- 
ment of the reed kind, the scale of which, 
though it includes every semitone within its 
extremes, is virtually defective. Its lowest 
note is E, below the F cliff, from which it 
is capable, in the hands of good solo per- 
formers, of ascending more than three oc- 
taves. Its powers through this compass are 
not every where equal ; the player, there- 
fore, has not a free choice in his keys, be- 
ing generally confined to those of C and F, 
which are the only keys in which the clari- 
net is heard to advantage. The music for 
this instrument is accordingly usually writ- 
ten in those keys. 
CLARION, a kind of trumpet, whose 
tube is narrower, and its tone acuter and 
shriller than that of the common trumpet. 
CLARO obscuro, or Clair obscure, in 
painting, the art of distributing to advan- 
tage the lights and shadows of a piece, both 
with regard to the easing of the eye, and 
tlie effect of the whole piece. See Paint- 
ing. 
CLASS, an appellation given to the most 
general subdivisions of any thing. Thus, 
in the Linnaean system of natural history, 
the animal creation is divided into six 
classes, riz. Mammalia, Aves, Amphibia, 
Pisces, Insecta, Vermes. 
Class, in botany, denotes the primary 
division of plants into large groups, each of 
which is to be subdivided, by a regular 
downward progression, in orders, or sec- 
tions as they are called by Tournefort, 
genera, and species, with occasional inter- 
mediate subdivisions, all subordinate to the 
division which stands immediately above 
them. So that the classes have been com- 
pared to the first layer of a truncated py- 
ramid, which increases gradually as it re- 
ceives the orders, genera, and occasional 
intermediate subdivisions, till at length it 
terminates in an immense base, consisting 
entirely of species. According to the de- 
finition of Linnmus, a class is founded on 
tlie agreement of the several genera with 
each other, in the parts of fructification, 
according to the principles of nature and 
art. It is observed, that, in the formation 
of classes, they should not be very nume- 
rous, and that their boundaiies should be 
strongly and distinctly marked. 
CLATHRUS, in botany, a genus of 
Fungi. Essential character : roundish, con- 
sisting of a reticular, windowed, hollow 
body; the ramifications connected on every 
CLA 
side. Linnaeus reckons only four species^ 
other botanists seven and eight. 
CLAVA, in natural history, a genus of 
Vermes Mollusca. Body fleshy, gregarious, 
clavate, and fixed by a round peduncle ; 
aperture single and vertical. Tliere is but 
one species, viz. C. parasitica, covered with 
pellucid conic erect spines. It inhabits the 
Baltic, on sea weeds, shell fish, and float- 
ing timber. Like the hydra, it possesses 
the power of dilating and contracting the 
mouth. See Hydra. 
CLAVARIA, in botany, a genus of 
Fungi ; one of the lowest order in the scale 
of vegetation, differing sometimes vei-y lit- 
tle in substance from the rotten wood 
whence it issues. It is a smooth oblong 
body, of one uniform substance. 
CLAVICLES, in anatomy, are two 
bones situated transversely and a little ob- 
liquely opposite to each other, at the supe- 
rior and anterior part of the thorax, between 
the scapula and sternum. 
CLAUSE signifies an article, or particu- ’ 
lar stipulation, in a contract, a charge or 
condition in a testament, &c. 
Thus we say, a derogatory clause, a penal 
clause, saving clause, codicillary clause, &c. 
CLAY. Any natural earthy mixture, 
which possesses plasticity and ductility when 
kneaded up with water, is in common lan- 
guage called a clay. All mineralogists, how- 
ever, have comprehended within the appeb 
lation, not only clays, properly so called, 
but a few other mineral substances nearly 
allied to some of the clays, and which be- 
come plastic by decomposition. Clay, how- 
ever, is by no means strictly a mineral spe- 
cies, being in most cases the result of 
the decomposition of other minerals. It 
seems advisable therefore to consider the 
property of plasticity as an essential cha- 
racter, and to exclude from the class of 
clays all earthy bodies that are destitute of it. 
Mineralogists have generally arranged all 
the plastic clays under two species, rather 
from the economical uses to which tliey are 
applied than according to their external 
characters, composition, or geological situa- 
tion. The first species is the white infu- 
sible porcelain clay, and the second contains 
all the rest compounded together, under 
the general appellation potter’s clay. We 
have, however, a different arrangement in 
Aikin’s dictionary, which we shall lay be- 
fore the reader. 
Essential character : plastic by intimate 
mixture with water. 
1. Porcelain clay. Its colour is generally 
reddish white, also greyish and yellowish 
