Z A M 



[277] 



Z E U 



" 3,. Z. debilis, or long-leaved zamia. 

 Leaflets linear, awnless, serrulate at the 

 tip from spreading, recurved, longer than 

 the channelled rachis ; stipe three-sided, 

 compressed, unarmed. Native of the 

 West Indies. 



" 4. Z. pungens, or needle zamia. 

 Leaflets awl-shaped, spreading, strict, 

 rigid, mucronate ; the outer margin of 

 the base rounded ; stipe roundish, un- 

 armed. Native of the Cape. 



" 5. Z. zycadis, or narrow-leaved za- 

 mia. Leaflets oblique, linear, lanceolate, 

 awl-shaped, hairy, curved, one, two, or 

 three-spined at the tip ; stipe unarmed. 

 Native of the Cape of Good Hope." 

 Encyclopedia Londinensis. 



Fossil zamise have been discovered in 

 the coal formation of Bohemia. In 

 Lindley and Button's Fossil Flora figures 

 of cones are given which are referred to 

 the genus Zamia, from the sandstone of 

 the Wealden formation at Yaverland, on 

 the south coast of the Isle of Wight. The 

 mode of inflorescence of the zamia is 

 splendidly shown in Prof. Buckland's 

 Bridgewater Treatise. 



ZA'MITK. A fossil zamia. M. Ad. Brong- 

 niart has referred the ' zamite,. or fossil 

 zamia, to a new genus, to which he has 

 assigned the name of Mantellia nidiformis. 



ZECH-STEIN. > The second member of the 



ZETCHSTEIN. $ red sandstone series, in 

 the ascending order. The zech-stein is a 

 calcareous deposit, or- magriesian lime- 

 stone, of a somewhat variable aspect ; it 

 is fossiliferous, and in it, as far as obser- 

 vations have yet gone, are found, for the 

 first time, those shells known by the name 

 of Productse. Some geologists are of 

 opinion that the connection between the 

 two formations of red sandstone and 

 zech-stein is so intimate, that the latter 

 may be regarded as a subordinate forma- 

 tion to the former. The zech-stein lies 

 immediately under the red sandstone and 

 above the marl slate, or kupfer schiefer, 

 of the magnesian limestone formation. It 

 is a deposit not widely spread over the 

 European area, and is principally known 

 in Germany and England. 



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

 and Xidog, a stone, Gr.) 

 1. Under this name some mineralogists 

 comprise eleven subgeriera of the mineral 

 genus zeolite, namely, 1. Trapezoidal 

 zeolite, or leucite ; 2. Dodecahedral zeo- 

 lite, or lapis lazuli ; 3. Hexahedral zeo- 

 lite, or analcime ; 4. Paratomous zeolite, 

 or cross-stone ; 5. Rhombohedrai zeolite, 

 or chabasite ; 6. Diatomous zeolite, or 

 laumonite ; 7. Prismatic zeolite, or me- 

 sotype ; 8. Prismatoidal zeolite, or stil- 

 bite ; 9. Hemiprismatic zeolite, or heu- 

 landite ; 10. Pyramidal zeolite, or apo- 



phyllite ; 11. Macrytopous zeolite, or 

 Brewsterite. These will all be found de- 

 scribed under their several names. 

 2. A translucent and, sometimes, trans- 

 parent mineral of a white, yellow, or 

 brownish-yellow colour, exhibiting double 

 refraction. Zeolite is electric by heat, 

 one summit of its prisms becoming posi- 

 tive 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 fascicular 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 terminations. Some 

 zeolites phosphoresce by friction. Before 

 the blow-pipe zeolite fuses with much 

 ebullition or intumescence into a whitish 

 spongy enamel, and it is from this pro- 

 perty 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", 

 chabasic, harmotome, and prehnite. Zeo- 

 lite most frequently occurs in amygdaloid, 

 basalt, greenstone, and clinkstone por- 

 phyry. It is also found in granite and 

 gneiss. Cleaveland. 



ZEOLI'TIC. Pertaining to zeolite ; con- 

 taining zeolite ; resembling zeolite. 



ZE'RO. (ztro, Fr. zero, It. ) This word is 

 of Italian derivation, and means a cipher 

 or 0. The expression is used to denote a 

 certain point or mark on the thermome- 

 trical scale. In the thermometers of 

 Celsius and Reaumur, zero is the point 

 at which water congeals. In Wedge- 

 wood's pyrometer, zero corresponds with 

 1077 of Fahrenheit's scale. The ques- 

 tion has been propounded, " at what de- 

 gree would a thermometer stand (suppos- 

 ing the thermometer capable of measuring 

 so low) were the body to which it is ap- 

 plied 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 zero at 2736 

 and 5803 below 0. 



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

 the thoracic order, having the head com- 

 pressed and sloping, the upper lip arched, 

 the tongue subulated, the body com- 

 pressed, thin, and shining, and the rays 

 of the first dorsal fin ending in filaments. 



