522 
PKOFESSOR HENRY A. MIERS; AN ENQUIRY INTO 
ceiitHns. of tHe solkl contain 224'4 grainnies of NaNO.^; 100 cub. centiins. of a 
48'8 per cent, solution contain GO’88 granunes NaNOg. The density of sodium 
nitrate in the crystal is, therefoi-e, about 3^- times that in the adjacent solution. 
AVithout knowing something more concerning the nature of the liquid, it is difficult 
to establish any relation between these numbers and the particular vicinal face 
produced. 
If we assume that not only the particles in the layer of liquid in immediate contact 
with the face, Init also those in consecutive layers for an appreciable distance, have 
the same arrangement as in tlie face itself; then, if the consecutive layers in the 
crystal are separated Ijy a distance D, and if A be the area of the elenientarv 
})arallelogram in the growing face, 
AD = constant = volume of the elementary parallelepiped in the lattice. 
And if consecutive layers in the liquid be separated by an interval X, then the 
volume of the elementary parallelepiped in the liquid is A Ah 
The ratio of the density of the material in the crystal to that in the liquid is 
therefore X/D, and in the substances considered al)ove this ciuantitv would be from 
17tto3i 
If the relative distances be calculated on the assumption that X be, as suggested 
above, not less than the least distance which separates adjacent particles in the 
crystal, the numbers obtained for vicinal faces inclined at 30' to the octahedron are 
not identical with these, l3ut are more than five times as great, whether the structure 
be the cube, the centred cube, or the cube witli centred faces ; and for vicinal faces 
inclined at only about 10' to the octahediT)n the disproportion is far greater. 
It will be noticed, however, that to assume any uniform distribution of the 
crystallisable material in the li(pud is to endow it with a crystalline structure before 
it solidifies. There is, perhaps, nothing impossilde in the idea that the material may 
be already arranging itself immediately before the act of crystallisation. (There is, 
however, no evidence that this is the case.) Under these conditions, the solution 
could not possess the (Ordinary prcjperties of a liquid, and, inter alia, might be 
expected to exhibit double refraction ; it was with this possibility in view that the 
strongly birefringent sodium nitrate was chosen above as a substance to be 
experimented upon, in the hope that evidence of birefringence might be detected in 
the solution in contact with the growung face; but no such evidence could be found 
by the method of total reflection within the crystal. 
To obtain anything like a correct estimate of the relative sizes of the meshes in 
the vicinal faces, and thei’efore of the distance which se})arates consecutive layers 
parallel to them, it would be necessary to measure their angles accurately not to 
minutes, but to seconds. To determine from the constitution or specific gravity of 
the liquid any relation between the arrangement of the particles in the vicinal face 
and in the solution, some assumption must be made concerning the successive layers 
in the latter. 
