140 Reports and Proceedings—Mineralogical Society. 
of one of the axes and the base as the zone containing the four poles, 
the usual anharmonic ratio is obtained. — Dr. G. T. Prior: The 
Meteorite of Daniels Kuil. The meteorite consists of nickeliferous. 
iron in large amounts, troilite, oldhamite, felspar, and enstatite, free 
from iron, and thus belongs to the exceptional Hvittis and Pillistfer 
group of chrondritic stones, to which also must be added the Khairpur 
meteorite, which contains notable amounts of oldhamite.—Dr. G. T. 
Prior: On the Relationship of Meteorites. Meteorites may be arranged 
by their chemical and mineral composition into the following six 
groups—(1) Bustee and Hvittis group, (2) Siderolites, (3) Cronstad 
group, consisting of chondrites containing over 10 per cent of nickeli- 
ferous iron, (4) Baroti group, consisting of chondrites containing less 
than 10 per cent of nickeliferous iron, (5) Chladnite group, including 
Chladnites, Angrites, Chassignites, Amphoterites, some Rodites, and 
probably some Chondrites containing little nickeliferous iron, 
(6) Eucrites, Nakhlites, Shergottites, Howardites, and some Rodites. 
It is suggested that from the first group the remaining stones have 
been derived by the interaction between oxidizing nickeliferous iron 
and enstatite, with consequent production of ferriferous olivine and 
bronzite, the formation of chondrules, and enrichment in nickel of the 
residual iron. The nickeliferous iron of the first three groups corre- 
sponds to the more common meteoric irons, such as the octahedrites and 
hexahedrites, containing less than 10 per cent of nickel, and that of 
the last three to nickel-rich Ataxites, containing more than 10 per cent. 
of nickel. The groups (2)-(6) contain progressively diminishing 
amounts of nickeliferous iron, which is increasingly rich in nickel, 
and have increasing amounts of ferrous oxide in the ferro-magnesium 
silicates, in which the ratio of magnesium to iron atoms approximates. 
in the case of group (2) to 7, of group (8) to 5, of group (4) to 34, of 
group (5) to 2, and of the last group to 1 or less.—Dr. J. W. Evans: 
The isolation of the directions-image of a section of a mineral in 
a rock-slice. In some optical investigations, e.g. the observation of 
the interference-figures of minerals in thin sections under the 
microscope, the determination of the angle of total reflection, and 
the measurement of crystal angles, the image studied is not that of 
the object, but is one in which every part corresponds to a direction 
in which light is transmitted, or in other words it is a directions- 
image. To prevent the effects of closely adjoining objects being 
blended all light except that traversing the object under investigation 
must be screened by a diaphragm placed near it or in a position 
conjugate with it. In an ordinary petrological microscope this may 
often be conveniently effected by placing the diaphragm below the 
condenser, so that the image of the aperture is seen in focus 
simultaneously with that of the object. The. best results are, 
however, obtained when the diaphragm is placed in the focus of the 
eve-piece, and, after it has been adjusted, the Becke lens placed above 
it. The same method may be employed with advantage in the other 
observations referred to, the instrument employed being constructed 
primarily as a microscope, and converted into a telescope by the 
addition of a lens, instead of vice versa as is the usual procedure.— 
Dr. J. W. Evans: A new method of determining the angular direction 
