CYANOSIS. 701 CYAXARES I. the face is bluish during an attack. It may bo permanent, as in a 'blue baby,' or child born with obstructed pulmonary circulation, or with a defect in the heart, by reason of which the arterial and the venous blood are constantly mixed. These children rarelj' live long. CYAN'OTYPE (Gk. Kiavoc,, kyaiios. dark- blue + TiJirof, tirpos, impression) PROCESS. A method of photograjjhy discovered by Sir John Herschel, in which certain cyanides are used. The process is based on the reduction of a ferric salt to a ferrous salt by the action of light in the presence of organic matter. In the practical application of the cyanotype process two solutions containing respectively one part of ammonium ferric citrate in four parts of water, and one part of potassium ferricyanide in four parts of water, are mixed, filtered, and preserved in a dark room. A good quality of paper is then floated for two minutes on the mixture and then left in a dark place to dry. If exposed under a negative or tracing to the sun for ten or twelve minutes and then washed in water and dried, the paper will show the picture or drawing in white on a blue ground. To obtain prints of a similar nature of warm brown tones, the mixture em- ployed is prepared by adding a solution of 50 grains of uranivmi sulphate in two ounces of water to a solution of 120 grains of ijotassium ferricyanide in two ounces of water. CY'ANU'RIC ACID (from cijanogen + uric, from Gk. ovpov, on run. urine), C3H3O.-N.,. An organic chemical compound produced by heating urea ; the latter, probably, being first trans- formed into biuret and cyanic acid, which then combine to form cyanuric acid, according to the following equation : C,H,0,N3 + NCOH - CHjOjN, -f NH, Biuret Cyanic Cyanuric Ammonia acid acid The most convenient method of preparing cyanuric acid is by heating the compound of cyanogen and bromine represeutcd by the for- mula CjNjBra with water at about 125° C, the formation of the acid taking place according to the following chemical equation: CsNjBrj + 3H,0 = C.,N,Hs03 + 3HBr. Cyanuric acid is a colorless crystalline sub- stance sparingly soluble in water and yielding, when heated, ordinary cyanic acid. Like cyanic acid (q.v. ), it is capable of yielding two series of derivatives, the study of which has led to as- signing to it two 'desmotropic' formulas, corre- sponding to the two different ways in which the acid may behave chemically, according to the transformations to which it may he subjected, and the conditions under which those transfor- mations may take place. These formulas repre- sent the structures of two difl'erent cyanuric acids, though only one can be actually prepared: HO- -C CO- I I N N ^ I Nil -H CO NH
CO I NH TO' Isocyanuric acid OH Normal cyanuric acid CY'ATHAS'PIS (Neo-Lat., from Gk. KiaSoc, kyathos, cup + AaTvi^, aspis, shield). The earli- est known fossil fish, specimens of which are found in the Upper Ludlow bone-bed of the Up- per Silurian of Kngland. The genus also con- tinues upward into the beds of the Old Red Sandstone of Kngland and Scotland, and it has been found in beds of (equivalent age in the Prov- ince of New Urunswick, Canada. It was one of the heavily armored fishes of the subclass Os- tracodcrmi ((j.v.). The specimens found arc all of small size, scarcely longer (ban one and one- half inches, and they consist of the dermal armor ol the head region only. This armor consists of two shields, which are, however, seldom found in apposition ; the dorsal shield of four plates, with the median plate the largest. This plate has on its under surface, in addition to the im- pressions of sujjposed auditory organs, the pit of the pineal body, and two lateral rows of impres- sions of branchial saes. The orI)its, or holes for llie eyes, are not well <listinguished on the an- lei-o-lateral angles of the shield. There were no jaws, for the mouth consisted of a mere opening between the anterior margins of the ventral and dorsal shields. The structure of the ventral shield is not well known. These shields protect- ed the head and possibly the anterior portion of the trunk; nothing whatever is known of the remainder of the body or the skeleton. Consult Lankester, "The Ceplialaspid;r," Moiior/raphs of the Palwontor/raphical Society (London, 18(iS and 1870). See Cephalaspis; Ostracodekmi ; Fish. CY'ATHOPHYL'LUM (Neo-Lat., from Gk. KiiaOog, lo/atlios, cup + ifivf./.ov, phyllon, leaf). A genus of fossil stony corals common in rocks of Middle Paleozoic age. The characters that distinguish this from other genera are of very obscure nature. The species, of which' there are about 100 in number, ranging through Ordovi- cian to Carboniferous rocks, vary greatly in form from small solitary individuals to large masses of closely compacted zooids, and their generic affinity can be determined only by study of thin sections under the microscope. The family of which C3'at!iophyllum is the type is a large one and includes many genera, of which the mo.st im- portant, Heliophyllum, Erido]iliylluni, Lithostro- tion, Omphyma. and Columiiaria. occurabundant- ly in the fossil coral reefs of the Lower and Mid- dle Devonian, and the (irboniferous. A recent reef-building coral, Moscleya, from Torres Straits, shows aifinities with the ancient Cyathophylloi- dea and serves to link this family with the mod- ern Astr:Fid:e. See CoRAL; CoRAL Island. CY AX' ARES I. (Gk. Kua^op?;?. Kyaxarea, OPers. Uvaxsatara, having good growth or pros- peritj-, Neo-Elam. Vakistara, Babylon Uvakvis- tar). King of the Medes from B.C. 625 to 585, or, according to other authorities, from B.C. 634 to 504. Herodotus ( i. 101-103) says he was the son of Phraortcs, and grandson of Deioces. wlu> was the founder of the Me<lian Eiwpirc. He de- scribes the pioneer work which Cy;ixares did in organizing a powerful and well-trained army, and alludes to an eclipse whieli took place in n.c. 610 when this monarch was at war with Alyattes, King of Lydia. A large part of Asia was brought under Cyaxarcs's sway, and he was successfully invading -Assyria and besieging Nineveh when his own kingdom of Media was invaded by the Scythians. In the combat which ensued the Scythians gained the day and held dominion over
