; Scheerer on Isomorphism. 61 
aware that minerals which we may look upon as different grades 
of saturation of one and the same radical, (be it simple or com- 
pound,) affect, 7 numerous instances, the same, or at any rate a 
very similar crystalline form.* 
' 4 14, Retinalite. _(Thomson.) 
21-07 Si : 13-22(R — 
ahr thine eo ae 2(R)* SitNa? Si. 
(R) = 18:86 Mg, 20:0 H, eet 0:30 Al, 0-84 loss. 
15. Some “ Serpentine-like Minerals.”  ( jhe! yt 
(1.) From Monte Rosa, 22°65 : 20-5 
 (2.) From Zermatt, 22-68 : 20°39. 
3.) From Col de Breona, 22°97 ; 19-30. 
Mean of the three analyses: 
99 ae 4 2 7 "1 a R j see 
Q277 : 20-24 aed Nia a Mle 
| In the first member of this formula, ( R) consists of magnesia, 
bis water and protoxyd of iron, whereas in the second it consists 
" chiefly only of magnesia. The formula may therefore, and in- 
& deed with greater propriety, be thus expressed : 2(R) ot ae Si. 
In which case it is quite analogous to that of retin 
16. Schillerspar. (Kéhler.) 
22°59 : 17°12 i OW. dene pes 
22-83 + 17-12 ‘ AR)? Si+(R)? Sit. 
The 1 : 1 atomic bases are according to two analyses = 25-86 
~26:16 Mz, 2°64 to 2:75 Ca, 10°92 Fe, 0°54 to 0°57 Mn, 12-43 #1. 
It appears more natural to assume that in the first member of this 
formula, 2(R)* Si, we should have a portion of the magnesia, and 
in addition thereto, the whole of the protoxyd of iron and the wa- 
| ter as } silicates; and in the second member of the formula, 
(R)? Siz, the remainder of the magnesia and the whole of the 
* One instance that occurs to me, is in Smaltine and Skutterudite. Aisles 
| the formula of the former is Co A s2, and that of the latter Co As3, saat t their _ 
, talline form is precisely alike. Another example is offered by the feldspars, whose 
atomic een rer may be thus expressed. 
R AI Si 
3:3: 4= Ano 
3:3: b= Labrador, Ryacolite. 
3:3: S8= Andes 
+3: Pata ua ele e, ' 
3:3:12—Orthoclase, Albite 
In accordance herewith, the Mert are cab: grades of saturation of a radi- 
See 
wo 
os Boe eoakoes of equal atoms of R and A 
t See Erdmann and Marchand’s J. f. P. ch. vol. xxxii, P. 499 ; cee Poms: Ann., 
vol. xlviii. 
i 
