Z E 



[ 467 ] 



Z E U 



above the marl slate, or kupfer 

 sehiefer, of the magnesian lime- 

 stone formation. It is a deposit 

 not widely spread over the Euro- 

 pean area, and is principally known 

 in Germany and England. Some 

 authors comprise a series of depo- 

 sits, formerly known to the German 

 miners under a variety of terms, 

 under the name of zechstein, these 

 were the Asche, Stinkstein, Rauch- 

 wacke, Zechstein, and Kupferschie- 

 fer. The Magnesian Limestone of 

 England may be regarded as the 

 equivalent of the Zechstein of Ger- 

 many. 



ZE'OLITE. (from e'w, to swell or foam, 

 and \i'0os, a stone, Gr.) The Me- 

 sotype of Haiiy : Kouphon Spath 

 of Mohs. 



1. Under this name, some miner- 

 alogists comprise eleven subgenera 

 of the mineral genus zeolite. 



2. A translucent and, sometimes, 

 transparent mineral of a white, 

 yellow, or brownish- yellow colour, 

 exhibiting double refraction. Zeo- 

 lite is rendered electric by heat, 

 one summit of its prisms becoming 

 positive and the other negative; 

 the latter is usually that summit 

 which was connected with the 

 gangue. It is found in distinct 

 crystals, whose surfaces have a 

 strong lustre, slightly pearly ; and 

 in masses composed of several fas- 

 cicular groups of minute crystals; 

 and in each group the crystals or 

 fibres diverge, or even radiate, from 

 one point, and at the surface fre- 

 quently appear distinct from each 

 other, or exhibit pyramidal termi- 

 nations. Some zeolites phosphor- 

 esce by friction. Before the blow- 

 pipe, zeolite fuses with much ebul- 

 lition or intumescence into a whitish 

 spongy enamel, and it is from this 

 property that it has obtained its 

 name. When reduced to powder 

 and thrown into nitric acid, it is 

 converted into a jelly in the course 

 of a few hours. This property of 



becoming gelatinous, as well as 

 that of becoming electric by heat, 

 sufficiently distinguish zeolite from 

 stilbite, analcime, chabasite, har- 

 motome, and prehnite. Zeolite 

 most frequently occurs in amygda- 

 loid, basalt, greenstone, and clink- 

 stone poryhyry. It is also found 

 in granite and gneiss. 



ZE'KO. (zero, Fr. zero, It.) This 

 word is of Italian derivation, and 

 means a cipher or 0. The expres- 

 sion is used to denote a certain 

 point or mark on the thermometri- 

 cal scale. In the thermometers of 

 Celsius and Reaumur, zero is the 

 point at which water congeals. In 

 Wedgewood's pyrometer, zero cor- 

 responds with 1077 of Fahrenheit's 

 scale. The question has been pro- 

 pounded, "at what degree would a 

 thermometer stand (supposing the 

 thermometer capable of measuring so 

 low) were the" body to which it is 

 applied totally deprived of caloric ? 

 or what degree of the thermometer 

 corresponds to the real zero?" This 

 question does not appear to have 

 ever been satisfactorily answered. 

 Dr. Crawford placed the real zero 

 1268 below 0. Mr. Kirwan fixed 

 the real zero at 1048 below 0. 

 Lavoisier and La Place placed the 

 real sero at 2736 and 5803 

 below 0. 



ZE'THUS. The name given by Pander 

 to a genus of trilobites, added by 

 himself to those previously des- 

 cribed. 



ZE'TJS. (zeus, Lat.) A genus of fishes 

 of the thoracic order, having the 

 head compressed and sloping, the 

 upper lip arched, the tongue subu- 

 lated, the body compressed, thin, 

 and shining, and the rays of the 

 first dorsal fin ending in filaments. 

 In Dr. Mantell's Geology of the 

 South-East of England, a species 

 of Zeus, found in the chalk, the 

 Zeus Lewesiensis, is beautifully 

 figured. This ichthyolite is from 

 six to eight inches long, and its 



