L I M E. 



31. Obtuft ptramlJiil dodecahihoii of 100' 24'.— The 

 •planes produced by ihc retrogradAtiou of the cryftalliiie 

 lainiiire replace the edges of the primitive rhomboid, but 

 iiiftead of being parallel to them, as in the precedinj; modili- 

 CHtions, they become narrower towards the fummit ot the 

 rhomboid. The two pyramids of this dodecahedron arc, like 

 thofe of No. 25, compofcd of ifofcelcs triangles, whence 

 the angles of their hnfe mull be upon a level. It has not yet 

 been obferved in. it- complete (late; but in a variety compoled 

 of its planes and thofe of Nos. 35 ?,nd 2, M. de Bournon has 

 feen it terminate the cry Hal in a very regular manner. It 

 has alfo been obfervyd in a cryftal in which the planes of 

 No. 2, and in another in which llioi'e of No. 36. arc predomi- 

 nant. 'J^ic cry llals exhibiting the planes of this modification 

 are rare, and have been found only in Dcrbyfliire and Cum- 

 berland. 



32. Obtufc pyramidal dodecahedron of lOl" 6'. — This has 

 not been feen complete, but in combination with the phinej 

 of feveral other moditicalions producing very complica'cd 

 <ry(lals. They occur in Dcrbylhire, but rarely. The 

 cleavage of this dodecahedron takes place at the bafe on the 

 lefs obtufe edges. 



33. Qbtufe pyramidal dodecahedron of gy''. — The cryftals 

 in which are feen the planes of this moditication occur but 

 leldom, and are ilUl more complicated than thofe with the 

 planes of the preceding modification. One of the two 

 cryftals figured by M. dc Bournoii comprehends 72, and 

 the other no lefs than 84 planes, of which thofe of the prif- 

 matic modification, No. 2, arc the principal ones. They 

 Were found in Derbyfhire. The cleavage of this dodecahe- 

 dron is the fame as that of the preceding modHkation. 



B. jlitite pyramidal dodecahedrons. — The following modifi- 

 cations, with the exception of Nos. 34, 56, 39. 48* and 50, 

 are all new. 



34. ylcutc pyramidal dodecahedron o/'88" ^'3'. — The planes 

 of tins dodecahedron are the refult of a decrement of the 

 cryllalline laminx along the edges of the bafe of tiie primitive 

 rhomboid: cleavage at the fummit on the more obtufe edges. 

 Thefe planes are marked u in Faiiy' figure of his chaux 

 carb. li^emince (pi. 27 fig. 49.) Befides in this combination, 

 (in which the planes of No. 36. are the moft prominent,) 

 M.de Bournon has obferved them witli the planes of Nos. 2, 

 Z9, and 34, in two cryftals from Cumberland, where alio 

 the complete dodecahedron has been found. The planes of 

 this modification are of rare occurrence. 



3J. Acute dodccahcdral pyramid of 78^ 40' — This is far 

 •lefs fcarce than the preccL.ing modificatifm, with which it 

 agrees in the nature of the decrement and the cleavage. 

 Has not yet been obferved in its complete ilate. Its planes 

 are reprefented in Haiiy's figure of chaux carb. afccndante 

 (pi. 27. fig. 44- «)' '" w-hich they are combined with tiiole of 

 Nos. 2 and II. Another cryftal has been defcribed by Haiiy, 

 under the name oi fjufquadniple (Ann. du Muf. vol. ii.), 

 which di!fers from the latter in having alfo traces of No 28. 

 The dodecahedron has not been feen in its complete Ilate, but 

 our author pofleffes cryftals in which the two pyramids are 

 ■feparated from one anotiier only by ftiort planes of the prif- 

 matic modification No. 2. Befides this, its planes have 

 been obferved in combination with fome other modifications. 

 Thefe cryftals have been found in Derbyiliire. 



36 ylcutc pyramidal dodecahedron o/" 48-' 22'. — This is 

 Haiiy's chaux carb. melajlatiqu: (pi. 4<S, iig. 70), a modifica- 

 tio:i which, both in its complete ftatc, and in conjunction 

 with the planes of other modifications, is of moft irequent 

 occurrence in the cryftals of calcareous ipar. We lliall 

 mention the more intexefting varieties. 



When, in the progrefs from the primitive rhomboid mto 

 this dodecahedron, only fmall planes of the former remain 

 at the top of the pyramid, it is the chaux carb. linairc (T 

 Haiiy (pi. 24. fig. 11.) Tlie complete dodecahedron is ftill 

 more common than this ; it is fometimes found with plants 

 of the pyramids unequal, and not meeting in a point ; alfo 

 as made. Combined with fmall planesof No. 2, it is Haiiy's 

 chaux carb. bifalterne (pi. 25. fig. 23); which likewife 

 occurs as made. When ihc^planes of the prifmatic variety 

 are more confiderable than in the jull-mentioned variety, 

 and, confequently, hexagonal, it is the chaux carb. prifnu: 

 of Haiiy (pi. 2). fig. 24.) ; this is very common. If, in addi- 

 tion to the latter, fmall planes of No. 4. are leen, it is t! e 

 chaux carb. annlogique prifmee of Haiiy (pi 26. fig. 35.) ; 

 from which the chaux carb. analo^iqtie disjoiiile (Haiiy, 

 pi. 26. fig. 38.) only differs in the magnitude of the planes 

 of Nos. 4 and 36. The combination of Nos. 2, 4, and 

 36, is alio fometimes feen in the fliape of that beau- 

 tiful made called " heart-fhaped calcareous fpar," and ex- 

 plained and figured by M. de Bournon. 'i'he prifm of 

 No. 2, having planes of this 36th modification, togetln r 

 with remains of the primitive planes at the fummils of the 

 pyramid, is Haiiy's chaux carb. bibinaire (pi. 25. 'fig. 26.) 

 In combination with the jji-ifni of No. 1, and with Nos. i 

 and ^-J, this dodecahedron is feldom found ; in the latter tlie 

 line which feparates the pyramidal planes from the prifm is 

 fometimes im.perceptiblc, fo that the cryftal appears com- 

 pofed of curvilinear planes. 



A variety, remarkable on account of its fimplicity, is the 

 chaux carb. analogigue (Haiiy pi. 26. fig. 34.) ; it is like- 

 wife compofed L>f the planes of this modilication, and thofe 

 of Nos. 2 and 4, forming altogether a cryftal of 24 trape- 

 zoidal planes, not unlike thole of the leucite, except that in 

 the former the planes are of three different dimtnfions. 



This modification is alfo of;cn feen in combination with 

 the planes of No. 1 1 ; the variety in whi.li thefe latter have 

 much increafed in fize at the expence of the former, is 

 Haiiy's chaux carb. blnoleriiaire (pi. 2 ;. fig 25.) ; the fame 

 cryftal is alfo obfervt-d as made. A fimilar variety, but 

 which contains alfo narrow planes of Nos. 4 and 17, is the 

 chiuix carb. doublaute of the fame cryftallographer, (pi. 27. 



The pyramidal variety of this modification with p'anes of 

 Nos 17 and 11, is Haiiy's chaux carb. progrejft-ve (pi. 27. 

 fig. 41.) ; and a fimilar one, but with the pbnes of 1 

 No. 2 inilead of II, is the fame auiiior's chaux carb. 

 emoujfee (pi. 26. fig. 40.) ; the latter occurs alfo as made. 



Many more combinations of the planes of this modification, 

 with thofe of others, are defcribed and figured by count 

 Bournon ; among others a cryftal, compofeo of feven modi- 

 fications, contains, in all, fixty planes, and another, com- 

 pofed of eleven modifications, exhibits no lefs than 96 planets. 

 The fame author has ilhiftrated this modification by 129 

 fignres. 



37. yseute pyramidal dodecahedron of 40' 14'. — Though 

 the dodcCdliedron of this modification is confidcrably more 

 acute than that of the preceding modification ; yet it ap- 

 pears to have hitherto been confounded with it. It has 

 been found in combination with the planes of the primitive 

 rhomboid, and thofe of Nos. 36, 2, and 11, and alfo ia its 

 complete ilate. The cryftals exhibiting this modification are 

 pretty large. They have been found only in the Dauphiiie 

 Alps of Loifan, and in Derbyfhire. 



38. P yrnimdal dodecahedron of ^f' 5'. — This might eafily 

 {je miftaken for the dodecahedron of t lie preceding modifica- 

 tion. It has not yet been obferved in its complete ftatc, but 



in 



