124 Scientific Intelligence. 



results and those of previous chemists, that they exemplify a new prin- 

 ciple in chemistry, which he names heteromerism, which is the reverse 

 of isomorphism, it implying a similarity of crystallization with a dif- 

 ferent proportion in the ingredients. Hermann obtains for the for- 

 mulas of 



Zoisite, 3f(2RO), (Si 2 )]+2[2(R 2 O 3 ), 3(Si 2 )] 



Bucklandite, 2[(2RO), (Si 2 )]+[2(R 2 O 3 ), 3(Si O 2 )] 

 Orthite, 3[(2RO), (Si 2 )]+[2(R 2 O 3 ), 3(S. O 2 )] 



He considers Pistacite as consisting of the Zoisite type and Buck- 

 landite type united, the green Arendal variety containing, according to 

 him, 2 atoms of Zoisite and 1 of Bucklandite ; and so on. 



Gerhardt observes that M. Hermann " doubtless preoccupied with 

 the idea that the oxyds represented by R 2 O 3 cannot replace the oxyds 

 RO in isomorphous substances, has entirely misunderstood the simplic- 

 ity of relation actually existing between the varieties of epidote. If he 

 had summed up the oxygen contained in all the oxyds and that of the 

 silica, he would have found in all cases the simple relation of 



1 : 1 



In fact, in the several cases mentioned the actual relations are as 

 follows, 2-94 : 3 03, 303 : 2*93, 301 : 304, 3-97 : 298, 2*91 : 287, 

 2-74 : 270, 274 : 269, 262 : 259, 2-56 : 255, 263 : 245, 205 : 2' 12. 

 All the epidotes have therefore the general formula* 



Si 2 4 (M 4 ) 



equal to [Si 2 2 -J-20M 2 ], "which comprises garnet, anorthite, olivine 

 and a great number of other minerals." In epidote M 4 is represent- 

 ed by variable quantities of alumina and peroxyd of iron on one side, 

 and lime, magnesia, protoxyd of iron, or of cerium on the other. Rep- 

 resenting the former by Mp? and the latter by M, the formulas of the 

 prominent varieties are as follows : 



Zoisite, Si 2 4 (M3 268 M 132 ) 



Pistacite, .... Si 2 O 4 (M^ 260 M 1 * 40 ) 



Bucklandite,. . . . Si 2 O 4 (M3 2 * 56 M 144 ) 



Orthite, .... Si 2 O 4 (iM£ 2 M 2 ) 



These formulas sustain the view of the isomorphism of these min- 

 erals. 



18. On Zygadite; by M. Breithaupt, (Pogg. Ann., Ixix, 429.) 

 Luster vitreous. Color red and yellowish white. Feebly transparent. 

 Density =2*511. Form of crystal a rhombic prism, and in all instan- 



^^ * m ' 



ces observed, macles. M. Planner has detected in it nothing but silica, 

 alumina and lithia. 



19. Bodenite, (Jour. f. Prakt. Chem., xliii, 207.)— This mineral 

 [alluded to in this Journal, vol. ii, p. 415,] has been analvzed by M. Th. 

 Kemdt with the following result.— Silica 2642, alumina 10*33, pro- 

 toxyd of iron 1205, yltria 347, lime 6*32, magnesia 2*33, protoxyd of 

 manganese 161, potash 1*21, soda 0-84, protoxyd of cerium 10*46, 

 protoxyd of lanthanum 7*56, water 301=99*27 : from which he de- 

 duces the formula Al 4 O 3 , Si 3 3 -{-9R 2 0, 2Si 3 O 3 . 



own 



silica Si 2 O 2 . The old notation is adopted in the preceding formulas, 



