901 
erystallisation at 1364°C.; in a second experiment crystallisation 
occurred at 1306° C., after undercooling to 1222°C., with a gradient 
of 3,°5 C., per minute. Here also the cooling-curves did not give 
in any case a reliable temperature for the equilibrinm liquid = solid : 
all thus obtained data appeared to be 230° or 240° C. lower than 
the real temperature of equilibrium for the transition solid 2 liquid. 
These experiments and the analogous ones in the case of the Ba- 
silicate and other objects, must prove, that even mechanical stirring 
of the liquid during its cooling, e.g. by means of electro-magnetic 
stirrers, as proposed by some investigators, is not able to produce 
the reaching of equilibrium in the case of such silicate in a sufficient 
way. Even under those circumstances the cooling-method remains 
an unreliable one. 
Strontium-metasilicate erystallises on slow cooling of the molten 
mass in glittering, irregularly bounded, flat crystals. In most cases 
these are penetration-twins or again more complicated aggregations, 
which are also produced in more rapid cooling of the liquid. Often 
the boundaries of the different united crystals are irregular, sometimes 
however clearly rectilinear. Every crystal shows a fine twin-striation, 
parallel to the extinction-directions. Very probably the silicate is 
monoclinic. 
On the border of the field in con- 
vergent polarized light a single 
branch of an hyperbola is visible. 
The refractive index in the direction 
of the striation is about: 1.590; 
perpendicular to it: 1.620. Some- 
times also long flat needles were 
found, with oblique extinction. 
The angle of extinction is about 
18° with respect to the length- 
direction of the needle. The crystals 
are very strongly birefringent; by 
Fig. 1. Strontium- Metasilicate, : ; 4 
molten and solidified. means of the immersion-method two 
refractive-indiees were determined to be: », = 8.595 + 0.003, and 
n, = 1.624 + 3.003. The double refraction is about; 0.029 to 0.030 ; 
at another time we found: n, = 1.590 + 0.003, and n, = 1,620 + 
+ 0.003. 
The specifie gravity of the solidified product was pycnometrically 
determined in ortho-chlorotoluene to be: d4o = 3.652 at 25°.1 C. 
By quenching the molten substance, heated to 1687° C., in 
mercury or water, a beautiful colonrless, and almost perfectly 
