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Dionysius I. King of Portugal, to animate his nobles against theMoors. The arms of this order are gules, patriarchal cross,charged with another cross argent, g. A rather military order in 1.1-vonia, instituted in 120 j, by Albert, bishop of Riga, to defendthe new Christians, who were daily converted in Livonia, butpersecuted bv the heathens. They wore on their cloaks a swordwith a cross over it, whence they were also denominated brothers;of the sword. |

CHROMA, [xjw/**, colour,] in music, a graceful manner of:singing. ]

Chroma, in rhetoric, a colouring, or elegance of expression, j

CllROMATiC, a kind of music which proceeds by several 1semitones in succession. Lor this denomination several causes Iare assigned, of winch the following appears to be the most satis -1factory. Xwyam may signify that shade of a colour by which it |melts into another, or what the French call nuance. In this sense jit will apply to semi-tones, which, being the smallest interval iallowed .in the diatonic scale, will most easily run one intoanother.

CHROMATICS, a branch of optics, which explains the se-veral properties of the colours of light and of natural bodies. SeeOptics and Colours.

CHROME, or CHROMIUM, a metal discovered by Vau-ciuelin. It exists in the state of an acid, combined with oxide oflead, in a beautiful mineral named red lead, found in Siberia, andwith regard to which very discordant analyses have been given bydifferent chemists. It has since been discovered in several mi-nerals. Vauquelin reduced the metallic acid which lie discoveredin it to the metallic state, and his researches have been confirmedby those of Klaproth and Gmelin. It derives its name from thesplendid and numerous colours which it presents in its saline com-binations. The native, chromate of lead, or the red lead of Si-beria, is generally crystallized in oblique tetrahedral prisms. Co-lour a fine aurora red ; lustre shining, and intermediate betweenadamantine and resinous; crystals translucid ; fracture uneven;specific gravity G.02(39. It decrepitates before the blow-pipe,.melts into a blackish sco'ria, and colours borax green by fusion.According to Vauquelin, it is composed of 57.10 of lead, G.SG ofoxygen, and 36.04 of chromic acid. There is found with thechromate of lead, a mineral of a green colour in minute crystals,which Vauquelin found to be composed of die oxides of chromeand lead, and which, as lie conjectures, lias probably originatedin the decomposition of the perfect chromate, from some processby which part of its oxygen lias been abstracted. Native chromateof iron lias more lately been found in the department of Var inFrance, and likewise in Siberia. This mineral is massive, of ablackish brown colour, with no great lustre and opaque ; fractureuneven ; specific gravity is 4.0. It is scarcely fusible before theblow-pipe, but with borax it melts into a glass of a fine green co-lour. According to an accurate analysis of it, it consists of 63.6of chromic acid, or perhaps rather oxide of chrome, and 36 otoxide of iron. Chrome lias been also found in smaller quantitiesin other minerals, particularly in some gems, of which it appearsto be the colouring principle. It exists in the emerald, in the staleof green oxide, and in the spinal ruby, in the state of acid. It isof a w hite colour, inclining to grey ; very brittle ; fracture pre-sents a radiated appearance, needles crossing in different direc-tions with interstices between them ; difficult of fusion, Exposedto tlie heat of the blow-pipe it does not melt. When fused by hav-ing been exposed to the intense heal necessary to. its reduction, it•presents crystalline filaments, which rise above the metallic mass.Chrome is not easily acted oil by the acids. Even when reducedto a fine puwder, and treated with concentrated boiling nitric acid,

it is oxvdized with much difficulty, and communicates to the acidonly a green tinge. Chrome, in the stale of acid, appears to b*more susceptible of combination, and this acid being obtainedwithout difficulty from its native combinations, its chemical rela-tions.have been more examined. Chromic acid is very solublein w-aler ; the taste of the solution is sharp and metallic ; it is of anorange-red colour; by evaporation, either spontaneous, or with agentle beat, it affortys crystals in long slender prisms, of a ruby-red colour. Tills acid combines with the alkalies, earths, and me-tallic oxides, form mg neutral sails which are named chromates.The combinations of this at id with metallic oxides are in generalpossessed of very beautiful colours, and are well adapted to formtlie finest paints. That with oxide of lead has an orange \ elloiv,of various shade ; that with mercury, a vermillionred ; with silver,a carmine red; with zinc and bismuth, tlie colours are yellow ;with copper, cobalt, and antimony, thev are dull.

CHROMATOGRAPHY, [from xi ul !* n and yz n f w > to write,]a treatise of colours ; tlie art of painting in colours.

CHROMATOPOIA, [from Xs w y - n >and to work,] the artof making and compounding colours.

CHRONIC, or CHRONICAL, among physicians, an appel-lation given to diseases that continue a longtime, in contradistinc-tion to those that soon terminate, and are called acute. Chronicaldiseases are, in general, neither attended with fever, nor any othersymptoms, portending a speedy termination of tlie complaint; andill this sense, they are opposed to acute, or inflammatory disor-ders. Physicians find tio small difficulty in drawing a precise lineof distinction between these affections; as the latter often change'into those of a chronic nature. Tissot derives the origin of inve-terate diseases from the following sources : I. Debility of the solidparts'of the body, either hereditary, or induced by adventitiouscauses; 2. Defective digestion, and weakness in the stomach ; 3.improper treatment, and imperfect resolution, of acute diseases ;and 4, Too great irritability, and other affections, of the'nervoussystem. From this view of the dimes, and the corresponding evi-dence of medical practitioners, it cannot be doubted that chronic,maladies are not only the most complicated, but also the most dif-ficult to be removed : Proteus-like, they appear under a thousanddifferent'forms, often exhaust the fortitude of tlie most patient,bailie tlie united efforts of the faculty, throw the unhappy personinto a state of despair, and deliver him over to all the arti-fices, and cunning of ignorant pretenders, who impose upon thecredulous victim, and close the scene of his delusion ! See Me-dicine.

CHRONICLE, [xfovuMv] in matters of literature, a species orkind of history, disposed according to the order of time, andagreeing in most respects with annals.

Chronicles, Books of, in the canon of scripture, two sacredbooks called by the Greeks ar-jptXforofaiva, that is, remains, addi-tions, or supplements, as containing many' circumstances omittedin the other historical books, in effect, tlie paralipomena, orchronicles, are an abridgment of sacred history to the return of thejews from tlie Babylonish captivity.

CIIRONODiX, [from Xv 0;0 >‘ and tiixw/xi, to shew,] 41 kind ofdial; an instrument to shew tlie time.

CHRONOGRAM, [xi”®', time, and yjttfx, to write,] an in-scription including tlie date of any action. Of this kind the follow-ing is an example :—

Gloria lausqtie, Deo, s;eC/.oi7hl7 in saccL'Ia sunto.

CHRONOLOGKR, [x 5 «v®-,time, andxoySP, doctrine,] lie thatstudies or explains the science of computing past time, or of rang-ing past events according to their proper yetrs.

CHRONOLOGY.

CHRONOLOGY, [xA®'. time, and i. «•/«>', doctrine,] tlie!■science <>f computing and adjusting the periods of time; as the ,revolution of tlie sun and moon ; and of computing time past, andreferring each event to tlie proper y ear. ;

Chronology consists oi two parts. The first treats of tlie pro-1vol. 1.—No. 45.

per measurement (if tune, and its several divisions; the second!,of fixing tlie dates ot tlie eicnls recorded in history, and rangingthem in the order in which they happened. Chronology, coiimvvrativelv speaking, is but of modern dale. Tits ancient pacts ap-pear to have been cut.rely unacquainted villi, d; and U-miut,.

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