154 
NATURE 
[APRIL 9, 1914 
sheep; Potchefstroom, in the Transvaal, to mealie 
growing, general agriculture, and cattle; Glen, near 
Bloomfontein, in the Orange Free State, to live stock 
and dry-land farming; Cedara, in Natal, to general 
farming and wattle growing. Provision is made at 
each institution for the regular in-college courses of 
instruction, for short courses, extension work, and 
also for experiments and research and the analysis of 
soils, manures, and other agricultural commodities. 
Additional buildings are being erected to meet the 
needs of the institutions, and their equipment gener- 
ally is being improved, while the staffs are being 
strengthened. 
SOCIETIES AND ACADEMIES. 
Geological Society, March 25.—Dr. A. Smith Wood- 
ward, president, in the chair.—Prof. J. W. Judd: The 
geology of Rockall. Rockall is a small isolated rock 
in mid-Atlantic, lying 184 miles west of St. Kilda, 
and, except in the calmest weather, is inaccessible. 
The rock rises from a bank (the ‘‘ Rockall Bank’’) 
upon which there are dangerous reefs. In 1810 Basil 
Hall, obtained a fragment from this rock, which later 
found its way into the collection of the Geological 
Society. More than thirty years afterwards, the 
specimen was recognised; it was then mislaid for 
another thirty years, and in 1895* was brought to the 
author. by the late Prof. T. Rupert Jones. He not 
only studied all the literature connected with Rockall, 
but was able to trace two other specimens of the 
rock, the loan of which he obtained and brought to 
me. They had been procured in 1868 during the 
survey of the North Atlantic. The microscopic study 
of these specimens shows that in Rockall there exist 
rocks of interest, not represented in our islands, but 
which have analogues in the Christiania district of 
Norway. These rocks consist essentially of three 
minerals—quartz, the felspar albite, and the rare 
soda-pyroxene egirite, with its dimorphous form 
acmite. Dredging operations have yielded specimens 
from the Rockall Bank. The abundance of bhasalt- 
fragments among the dredgings suggests the possi- 
bility of Rockall belonging to the same petrographical 
province as St. Kilda, Iceland, the Inner Hebrides, 
and the north of Ireland. The existence of borolanite 
and other alkaline rocks in the northern Highlands 
suggests the possibility of Rockall being the western 
extension of a much older province. Some months 
ago Prof. Iddings and Dr. Washington represented 
to the author the desirability of a detailed analysis of 
this rock. One of the two fragments available was 
sent to America, and the following paper gives the 
result of its study by Dr. Washington.—Dr. Henry S. 
Washington ; The composition of Rockallite. A petro- 
graphical account is given, with reference to the 
influence of the constituent minerals upon the bulk- 
analysis. Rockallite has a_ fine-grained granitic 
structure, and is composed of about equal amounts 
of colourless quartz, alkaline felspar, and _ soda- 
pyroxene. The pyroxene is of two kinds: a bright 
grass-green exgirite and a pale yellowish-brown acmite. 
Some zircon is present. A chemical analysis has 
been made, zirconia and the rare earths being 
especially looked for. Several new points of interest 
have presented themselves. The outstanding features 
appear to be the high percentages of silica, ferric 
oxide, and soda, and the low percentages of alumina, 
ferrous oxide, magnesia, lime, and potash. The in- 
terest of the new analysis, however, lies in the detec- 
tion of zirconia and cerium oxide in large amounts : 
the percentage of cerium oxide being larger than that 
from any known igneous rock, with the exception of 
the nepheline-syenite from Almunge in Sweden. The 
NO; 2310; VOL» 93)| 
norm has been calculated from the old and the new > 
analyses, and the author finds that the rock falls into 
the subrang rockallose with the general symbol 
III. 3. 1. 5. These analyses are the only representa- 
tives of the subrang rockallose among the 8000 
analyses of igneous rocks that the author has now 
collected. It is proved that the zirconia and cerium 
oxide enter into the composition of the pyroxenes. 
CAMBRIDGE. 
Philosophical Society, February 23.—Sir J. J. Thom- 
son in the chair.—Dr. Searle: (1) Determination of 
the effective aperture of the stop of a photographic 
lens; (2) experiments with a prism of small angle.— 
A. E, Oxley: (1) The molecular field in diamagnetic 
substances (preliminary note); (2) the internal mole- 
cular field, which has been shown by the author to 
exist in diamagnetic substances, is applied to account 
for the abnormally high values of the specific heat of 
such substances in the neighbourhood of the fusion 
point.—Major P. A. Macmahon;: The superior and in- 
ferior indices of permutations.—N. Wiener: A simpli- 
fication of the logic of relations.—R. Hargreaves: The 
domains of steady motion for a liquid ellipsoid, and the 
oscillations of the Jacobian figure.—J. E. Purvis and 
E. H. Black: The oxygen content of the river Cam 
before and after receiving the Cambridge sewage 
effluent. 
March 9.—Dr. Shipley, president, in the chair.— 
Prof. Wood and G. Udny Yule: A statistical study of 
feeding trials with oxen and sheep. The authors have 
studied statistically the results of 400 feeding trials 
with oxen and sheep collected and tabulated by Ingle 
in the Journal of the Highland and Agricultural 
Society, 1tg09-1c. They find that as the amount of 
food is increased above that required for maintenance 
the successive increases in live weight become smaller 
until a limiting value is reached.—G. Udny Yule: 
Fluctuations of sampling in Mendelian ratios. The 
author compares the fluctuations observed, e.g. in the 
proportion of recessives in F,, in the seeds borne by 
individual plants, or in individual litters, with the fluc- 
tuations to be expected on the theory of random 
sampling. For the most part the agreement, in the 
examples taken, is good and in some cases striking.— 
M. S. Pease: Inheritance in Brassice.—G. Udny 
Yule and F. L. Engledow: The determination of the 
best value of the coupling ratio from a given set of 
data.—F. L. Engledow: A case of repulsion in wheat. 
The characters concerned are ‘“‘roughness’’ and 
‘blackness "’ of the chaff. In a cross between ‘‘ smooth 
black” and ‘trough white”’ the numbers in the second 
generation indicate a repulsion on the 1: 3: 3: 1 basis. 
—T. Rigg: Soil and crop relations in the Biggleswade 
market garden area. The author has conducted a soil 
and crop survey of this district. The soils have been 
classified and the extent of each soil formation has 
been determined. Maps were shown illustrating the 
relationship of the soil formations to the geological 
formations.—H. A. D. Neville: Digestibility of pento- 
sans. Rats were fed on a basal diet, to which was 
afterwards added a quantity of some pentosan sub- 
stance, such as (a) gum, (b) a vegetable mucilage, or 
(c) the pentosan constituent of a cereal straw. The 
pentosans of (c) almost entirely disappeared in the 
animal, those of (b) were almost wholly rejected, while 
those of (a) occupied an intermediate position. The 
results support the idea that the diverse opinions held 
on the food value of the pentosans have arisen by 
reason of the analytical method used yielding furfur- 
aldehyde from differently constituted substances or 
from substances containing pentose sugar molecules 
differently united in the parent substance.—W. H. 
Parker : A case of correlation in wheat. <A high cor- 
