94 J. D. Dana on a connection between 
SnO2. A metal in the different states R, Rz, R:, has, accord 
ingly, the same isomorphic power; and so also, 2R, 2Ra, 2R4; 
and 8R, 8Rz, 8R1. Hence under the principle explained— 
RO, R20, RO should be alike isometric in crystallization. 
2(RO), 2(Rz0), 2(RyO) may be tetragonal “ # 
3(RO), 3(Rg0), 3(R4O) may be hexagonal . 
chance for a comparison, like that with respect to carbon. 
Anatase is probably TiO*, and rutile Ti?O*, the density of the 
tinct: that Fe in the alpha state is related to all other metals 
um 
in alumina: that Fe, Mn, Cu, Pb in the gamma state should be 
classed with Ti, Sn. : 
elles Aid is given ee principle explained toward determin 
ing-In many cases what are the accessory 
ngredients in a compound, and thence what should be rega 
as its true constitution. 
6. Crystallogeny hereby learns that quadratic or tetragonal sym 
metry tn crystals depends on quadrati 
_ # For this inference with i ; ‘in the di I 
am intel t Prt with regard to the equivalent of carbon in the diamond 
views 
a oi ° 
a 
and what the dominant | 
tic symmetry, or the recurrence — : 
G. F. Barker, who offered it while I was explaining to bit “a 
in this papers 66 ae : : 
