518 
PEOFESSOR HENRY A. MIERS: AN ENQUIRY INTO 
aiilFassen, welche aber, nach cler Terminologie Jeeofejew’s, zii verschiedenen ‘ zusam- 
mengehauften ’ Individuen gehoren, und zwar deswegen, well die Winkel dieser 
Flachen nicht genaii den idealen Grossen, welche die Symmetrie erfordert, entsprechen. 
Diese Ansicht ist das Residtat eines falschen Begriffes vom Kiystalle als von einem 
Individnnra, das sich nnbedingt durch einen bestimmten Anfangspunkt des Wachs- 
thnms auszeichnet. Wir konnen den Krystall nur dann als aus mehreren Individuen 
bestehend betrachten, wenn mail in ihm mehrere solche Punkte nachweisen kann. 
Andererseits erhidt man den Begriff ‘ Zusammenhaufimgen der Individuen ’ in Folge 
einer einseitigen Vorstellung vom Krystalle, wenn man ihn nur als geometrischen 
Korper betrachtet. Beide Ansichten liber die Vicinalflachen haben nur dadurch 
entstehen konnen, dass man den Krystall an und flir sich, unabhangig von dem 
Medium, in welchem er sich bildet, betrachtete.” 
Now the question whether the vicinal faces are due to the concentration streams is 
one in which direct ajDpeal can be made to exiDeriment. I have mentioned above the 
experiments which I made in 1894 with the object of eliminating possible differences 
of concentration in the mother-liquor. Small crystals of potassium-alum were 
suspended from the arms of a wooden vane, which was kept rotating in a concentrated 
solution of the salt for several hours by means of clockwork. No efiect whatever 
seemed to be produced upon the crystals either as regards the presence or absence of 
vicinal faces or the brilliancy and smoothness of the crystals. 
Becently I have made similar, but more precise, experiments in order to ascertain 
whether the stillness or violent motion of the liquid have any efiect in altering the 
angles of the vicinal forms. 
The experiments were made in two ways : a crystal, having been mounted in the 
platinum clip, was allowed to grow until well developed, and was measured in the 
solution; without being withdrawn from the solution, it was then attached to a 
vertical spindle and kept rotating for several hours by means of a small water-motor, 
and was then measured again. In other experiments the trough of liquid was placed 
upon a turn-table and set rotating, the crystal remaining fixed within it. 
Experiments upon Potassium-alum Crystallisimj in an Agitated Solution. 
An octahedron yielded three well defined vicinal planes upon each of two 
octahedron faces A and B; the angle between one facet a and the edge of the other 
facets, /3, y, was measured as in fig. 10. 
A, : A^^ = 0° 30'; B, : B^^ = 0° 31'. 
At 4 p.M. the crystal was set rotating, the temperature being 19° C. 
At 7.30 p.M., t = 11°, the crystal was stopped and measured, and gave 
A, : A,^0° 48'; B„ : B,, = 0° 31'; 
but these were now accompanied by other and less distinct images. 
