CHO 
order. Natural order of Compositas Semi- 
flosculosa;. Cichoraceee, Jussieu. Essential 
character : calyx calycled ; floscules in 
ipany rows ; seeds muricated ; pappus sim- 
ple, stipitated. There are three species. 
CHONDROPTERIGIOUS, a term ap- 
plied by the Linnaeau system to an order of 
fjshps with cartiiaginous gills. Dr. Shaw, 
and other naturalists, have upited the Bran- 
chiostegi and Chondropterygii under the 
general title of Cartilaginei. Linnaaus se- 
parated the cartilaginous from the other 
fishes, and placed them in the class Amphi- 
bia, where they constituted the order Nan- 
tes. This distribution was made under the 
supposition of the cartilaginous fishes being 
furn^hed both with lungs and gills. The 
supposed lungs, however, have been since 
ascertained by naturalists to be only a mo- 
dification of the gills, and it, therefore, now 
appears that this cartilaginous tribe are in 
reality fishes, differing principally, if not en- 
tirely, from otlier fishes, in having a cartila- 
ginous skeleton. They differ from the ge- 
nerality of other fishes, in having gills desti- 
tute of bony rays, or in the gills being car- 
tilaginous, and they are deficient for the 
most part at least of obvious scales, those 
being either very deciduous, minute, or so 
deeply imbedded in the skin, as to be 
scarcely visible. In many of the cartilagi- 
pous fishes there is not tlie slightest appear- 
ance of scales on the surface of the skin. 
The Chondropterigii genera are 
Acipenser Chimajra Gastrobranchus 
Petromyzor Pristis Raia 
Squalus: which see. 
■ X’ — 
CHORD of an arch is a right line joining 
the extremes of that arch. 
Chord of the complement of an arch, the 
chord that subtends the rest of the arch, or 
so much as makes up the arch a semicircle. 
It is demonstrated in geometry, that the 
radius bisecting the chord also bisects the 
arch, and is perpendicular to the chord. 
From hence may be deduced these pro- 
blems: 1. To make a circle pass through 
any three given points, not lying in a right 
line. 2. To find the centre of any circle. 
3. To complete a circle from an arch given. 
4. To describe a circle about any triangle 
given. 
Chords, line of, one of the lines of the 
sector and plane scale. See Instruments, 
mathematical. 
Chords, or Cords, in music, are strings, 
by the vibration of which the sensation of 
^oiuid is excited, and by the divisions of 
CHO 
which the several degrees of tune are de' 
termined. 
The chords of musical instruments are 
ordinarily made of cat-gut; though some 
are made of brass or iron wire, as those of 
hai-psichords,spinnets, &c. Chords of gold- 
wire in harpsichords would yield a sound al- 
most twice as strong as those of brass ; and 
those of steel a feebler sound than tlwse of 
brass, as being both less heavy and less 
ductile. 
The rules for dividing 'Chords so as to con- 
stitute any given interval, are as follow : to 
assign such part of a chord A B as shall con- 
stitute any concord ; for example, a fifth, 
or any other interval, with the whole chord : 
divide the line A B info as many parts as 
the greatest number of the interval has 
units ; thus the fifth being 2 : 3, the line is 
divided into 
C 
A. L_ ! B 
three parts : of these take as many as the 
lesser number 2 = A C, then is A C the 
part sought; that is, two lines whose 
lengths are to each other as A B to A C, 
make a fifth. Hence if it be required to 
find several different sections of the line 
A B, for instance, such as shall be octave, 
fifth, or third greater ; reduce the given ra- 
tios 1:2, 2:3, and 4 : o to one fundamen- 
tal, the series becomes 30 : 24, 20 : 15, the 
fundamental is 30, and the sections sought 
are 24 the third greater, 20 the fifth, and 
15 the octave. 
To divide a chord A B in the most sim- 
ple manner, so as to exhibit all tire ori- 
ginal concords. Divide the line into twm 
equal parts at C, and subdivide the part 
C D into equal parts at D, and again the part 
C D into equal parts at E. 
C E D 
Here A C : A B is an octave, A C : A D 
a fifth, AD : A B a fourth, A C : A E a thirA 
greater; AE:AD a third less; AE:EB 
a sixth greater ; A E : AB a sixth less. 
Chord is also used in music for the note 
or tone to be touched or sounded : in this 
sense the fifth is said to consist of five 
phprds or sounds. 
CHORDOSTYLUM, in botany, a ge- 
nus of the Cryptogamia Fungi. Fungus 
tenacious; on a very long, tough, slightly 
branched stem; head globular, somewhat 
deciduous, bearing the seeds. There ai’e 
five specie.s. 
