386 Scheerer on Isomorphism. 
Under these circumstances the idea is forced upon us, that these 
two minerals, cordierite and aspasiolite, are ¢somorphous, and that 
this isomorphism is founded upon the power which a certain 
amount of water has to replace a certain quantity of magnesia. 
Calculation informs us that in this case, three equivalents of water 
would replace one equivalent of magnesia. Assuming this to be 
the case, and substituting magnesia* in accordance therewith for 
the amount of water contained in aspasiolite, we should obtain 
the following ratio of oxygen for this mineral, 
Si Al R 
26:18 : 15:12 : 5-63; 
whereas the corresponding ratio for the Kidgerde cordierite was, 
oe been shown, 26°20 : 15°26: 5-48. Both these ratios of 
n pri therefore, by this substitution, all but precisely 
pot ag Even ass ‘that in aspasiolite a minute portion of 
its iron (about half its amount) occurs as the peroxyd, would 
modify the above ratio but very immiaterially ; in that case we 
should have the num 
Si R 
26°18 : 15 52; 5:37, 
thus fais igri. to the ratio of oxygen that we arrive at in 
ning the are quantity of iron in the Kragerée cordierite 
as a pee by w ren as before stated, the numbers we obtain 
are, 26:20 : 15°64: 
hatever view sly are disposed to adopt therefore, in this re- 
pee the result in every case is, that the similar crystalline forms 
olite and in cordierite, is to be explained upon the as- 
fnvtion that three equivalents of water can replace isomorphi- 
ally one equivalent of magnesia. So striking a result as this, 
in the present want of any analogous observations, could not, it 
is self-evident, although borne out by facts, be at once looked up- 
on as thoroughly established ; and I therefore set about investiga- 
g the truth of the matter from other points of view, to the ut- 
iticat in my power.t 
Mimi ee 
* That is to say, in the proportion of 3EZ to 1Mg, or in other words of 3X 11243= 
357-44 =O 706 Part 
by weight of magnesia. For the 6-73 per cent. of water coutaiion in aspasiolite, 
according to my analysis, we must hanes nubetisets 673X 07 “15 per cent. 
od magnesia. 
337-44 to 25835; therefore for every part by weight of water, 
necessa 
ae then to calculate the is en of the quant 
that is requisite is to divide og resis _ ih «ty Bee gen Bo of the er wi & three, and 
to add the he ong 
t ich means, 
in the example before us, the ahd laaaae yee t oxygen ny saci ai X5-98=5'63, 
as Bed find it given above. aseiaes Nai wi 
+ Something | ig t! test og: Scheerer’s views 
Lam altogether mistaken, been [allude to what Prof. Fuchs Poche ay 
ative toa certain quantity of water replacing soda.—W. G. L. 
