C H R 
C H R 
C,f plants ; and in the natural method ranking 
•untler the 49th order, composite. The re- 
ceptacle is naked; the calyx calyculated ; 
the pappus simple and stalked; the llorets 
in a manifold series. There are three species. 
CHORD, in geometry, a right line drawn 
from one part of an arcli of a circle to the 
other. See Geometry-. 
Chords, Line of one of the lines of the 
sector and plane scale. See Mathemati- 
cal Instruments. 
Chords, or Cords, in music, are strings, 
by the vibration of which the sensation of 
sound is excited, and by the divisions of 
which the several degrees of tune are deter- 
mined. 
To find the number of vibrations made by a 
musical chord, or string, in a given time, hav- 
ing its weight, length, and tension, given. Let 
/ he the length of the chord in feet; 1 its weight, 
or rather a small weight fixed to the middle, 
and equal to that of the whole chord ; and tv 
the tension, or a weight by which the chord is 
stretched. Then the time of on e vibration will 
be expressed by ^ j ^ ; consequently 
the number of vibrations per second is equal to 
JL. K / Thus, if tv = 28800, or the 
ii \/ — T~ 
tension equal to 28800 times the weight of the 
chord, and the length of it three feet, then the 
last theorem gives 354 nearly for the number of 
vibrations made in each second of time. But if 
tu = 14400, there would be only 250 vibrations 
per second; and if tv — 288, there would be 
muc vibrations per second. 
CHORIAMBjJS, in autient poetry, a foot 
consisting of fo t syllables, whereof the first 
and last are long, and the two middle ones 
are short ; or, which is the same thing, it is 
made up of a Irocharis and iambus : such is 
the word nobili’tas. 
CHOllOG RAPHY, the art of making a 
map of some country or province. 
Chorography differs from geography, as 
the. description of a particular country does 
from that of the whole earth ; and from to- 
pography, as the description of a country 
differs from that of a town or district. 
CHOSE, in action, is an incorporeal 
thing, and only a right, as an annuity, bond, 
covenant, &c. and generally all causes of 
suit, for anv duty or wrong, are accounted 
choses in action. " Choses in action may be 
also called choses in suspense, as having no 
real existence, and not being properly in our 
possession. 
CHRIST, order of, a military order, 
founded by Dionysius T. king of 1 ortugal, to 
animate his. nobles against the Moors. 
The arms of this order are gules, a patri- 
archal cross, charged with another cross ar- 
gent: they had their residence at lirst at Cas- 
tromarin, afterwards they removed to the 
city of Thomar, as being nearer to the Moors 
of Andalusia and Estremadura. 
CHROMATIC, in the antient music, the 
second of the three kinds into which the con- 
sonant intervals were subdivided into their 
•concinnous parts. The other kinds are en- 
harmonic and diatonic. 
CHROMATICS, that part of optics 
which explains the several properties of co- 
lours. See Optics. 
CHRONIC, or Chronical, among phy- 
sicians, an appellation given to diseases that 
continue a long time, in contradistinction to 
those that soon terminate and are called 
acute. See Medicine. 
CHRONICLE, in matters of literature, a 
species or kind of history, disposed according 
to the order of time, and agreeing in most 
respects with annals. M he word chronicle is 
now become obsolete, being seldom used ex- 
cept in speaking of the old English Histories, 
as Store’s chronicle, Holingshed’s chronicle, 
&c. 
CHRONOLOGY, the art of measuring 
and distinguishing time ; with the doctrines 
of dates, epochs, anas, Ac. is a science of the 
utmost importance for the right: understand- 
ing of history. It depends and is founded on 
1st, astronomical observations, especially ot 
the eclipses of the sun and moon, combined 
with calculations of the year, and airas of dif- 
ferent nations. 2dly, On the testimonies of 
credible authors. 3dly, Such epochs in his- 
tory as have never been controverted. 4tlily, 
Antient medals, coins, monuments, and in- 
scriptions. 
Sir Isaac Newton has shewn that the chro- 
nology of antient kingdoms is involved in the 
greatest uncertainty ; and that the Europeans 
had no chronology before the existence of 
the Persian empire, or 536 years before 
Christ, when Cyrus conquered Darius : that 
the antiquities of the Greeks are full of tables, 
till this period, and that after this time seve- 
ral Greek historians introduced the compu- 
tation by generations. 
The chronology of the Latins was still 
more uncertain : " their old records having 
been burnt by the Gauls 120 years after the 
expulsion of their kings, and 388 before the 
birth of Christ. The chronologers of Gaul, 
Spain, Germany, Scythia, Sweden, Britain, 
and Ireland, are of a still later date ; for 
Scythia beyond the Danube had no letters 
till Hfyhilas, their bishop, formed them, 
about the year 276. Germany had none till 
it received them from the western empire of 
the Latins about the year 400. The Huns 
had none in the days of Procopius, about the 
year 526 ; and Sweden and Norway receiv- 
ed them still later. 
Sir Isaac Newton, after a general account 
of the obscurity and defects of the antient 
chronology, observes, that though many ot 
the antients computed by successions and 
generations, yet the Egyptians, Greeks, and 
Latins, reckoned the reigns ot kings equal to 
generations of men, and three of them to a 
hundred, and sometimes to 120 years, and 
this was the foundation of their technical 
chronology. He then proceeds, from the 
ordinary course of nature, and a detail of 
historical facts, to shew the difference be- 
tween reigns and generations; and that, 
though a generation from father to son may 
at an average be reckoned about 33 years, 
or three of them equal to 100 years, yet, 
when thev are taken by the eldest sons, 
three of them cannot be estimated at more 
than about 75 or SO years ; and the reigns 
of kings are still shorter ; so that 18 or 20 
years may be allowed as a just medium. Sir 
Isaac then fixes on four remarkable periods, 
viz. the return of the Heraclida: into the 
Peloponnesus, the taking of Troy, the Ar- 
gonautic expedition, and the return ot Se- 
sostris into Egypt after his wars in Thrace; 
and he settles the epoch of each by the true 
value of a generation. To instance only 
his estimate of that of the Argonautic expe- 
dition : Having fixed the return of tin- lle- 
raciidie to about the 159th year after the 
■ death of Solomon, and the destruction ot 
Troy to about the 76fh year after that 
period, he observes, that Hercules the Ai 
gonaut was the father of l lyllus, the father ot 
Cleruius, the father ; of' Aristomachus, the la- 
ther of Aristodemus, who conducted the 
Heraclida: into Peloponnesus : so that, reck- 
oning by the chiefs of the family, their return 
was four arm-rations later than the Argonau- 
tic expedition, which therefore happened 
about 43 years after the death of Solomon. 
This is farther confirmed by another argu- 
meht : iEsculapius and Hercules were Argo- 
nauts : Hippocrates was the 1 8th inclusively 
from the former by the father’s side, and the 
19th from the latter by the mother’s side : 
now, allowing 28 or 30 years to each ot them, 
the 17 intervals by the father, and the 1$ 
intervals by the mother, will on a medium 
give 507 years; and these, reckoning back 
- from the commencement of the. Pelopon- 
nesian war, or the 431st year before Christ, 
when Hippocrates began to flourish, will 
place the Argonautic expedition in the 43a 
year after the death of Solomon, or 937 
years before Christ. 
The other kind of reasoning by which sir 
Isaac Newton endeavours to establish this 
epoch, is purely astronomical. The sphere 
was formed by Chiron and Musaus tor the 
use of the Argonautic expedition, as is plam- 
1 -. shewn by several of the asterisms refei- 
ing to that event : and at the time of the 
expedition the cardinal points of the equi- 
noxes and solstices were placed in the 
middle of the constellations Aries, Cancer, 
Chela*, and Capricorn. This point is esta- 
blished from the consideration of the antient 
Greek calendar, which consisted of 12 lunar 
months, and eacli month of 30 days, which 
required an intercalary month. Of course 
this lunisolar year, with the intercalary 
month, began sometimes a week or two be- 
fore or after the equinox or solstices : and 
hence the first astronomers were led to 
the before-mentioned disposition of the 
equinoxes unci solstices: und. that this 
was really the case, is confirmed by 
the testimonies of Eudoxus, Aratus, and Hip- 
parchus. Upon these principles sir Isaac 
proceeds to argue .in the following manner. 
The equinoctial colure in the end of the year 
1689 cut the ecliptic in 8 6° 44' ; and by 
this reckoning the equinox, had then gone 
back 36° 44' since the time of the Argonau- 
tic expedition. But it recedes 50' in a year, 
or 1° in 72 years, and consequently 36° 44 
in 2645 years ; and this, counted backwards 
from the beginning of 1690, " ill place this 
expedition about 25 years utter the death of 
Solomon. Rut as there is no necessity for 
allowing that the middle of the constellations, 
according to the general account of the an- 
tients, should be precisely the middle be* 
tween the prima Arietis and ultima Cauda*, 
our author proceeds to “ examine what were 
those stars through which Eudoxus made the 
colures to pass in the primitive sphere, and 
in this way to fix the position of the cardinal 
points.” Now from the mean of live places 
he finds, that the great circle, which in the 
primitive sphere, described by Eudoxus, or 
which at the time of the Argonautic expedi- 
tion, was the equinoctial colure, did in the 
