216 

NATURE 
[APRIL 22, 1915 

and vertical disturbances that will cause marked 
oscillations of unifilar and bifilar magnets and mag- 
netic balances; and that, if the periods of the earth- 
quake-vibrations should approximate to any of these 
periods, they may cause the magnets to oscillate. 
Prof. Reid concludes that the broadening, blurring, 
or interruption of the magnetic trace at the time of 
earthquakes may be due to oscillation of the suspended 
magnets by purely mechanical vibrations, and does 
not require us to assume the existence of real magnetic 
forces or electric currents. 
Mr. N. L. Bowen (Amer. Journ. Sci., vol. xxxix., 
1915, p- 175) describes and illustrates several interest- 
ing experiments which show that crystals separating 
from a molten silicate mixture tend to accumulate 
by gravitation in the lower layers of the mass. He 
thus gives strong support to Charles Darwin’s view 
of gravitation as a factor in the differentiation of 
igneous rocks. Crystals of olivine have been gathered 
towards the bottom of a crucible, those in the lowest 
layers being smaller than those above them, since the 
latter have fallen through a greater depth of liquid. 
Both olivine and pyroxene crystals induce during cool- 
ing the formation of coats of amphibole round them. 
Seeing how quartz in lavas may become coated by a 
deposit of pyroxene, there is clearly room for further 
research as to these reaction-zones. The author has 
succeeded in separating tridymite in more highly 
siliceous mixtures, the crystals becoming in this case 
concentrated upwards by flotation. 
Tue January issue of the Proceedings of the Academy 
of Sciences of Philadelphia contains a summary, in 
French, by Mr. Stanislas Meunier of his views with 
regard to the general theory of glacial phenomena and 
the origin of polished and striated pebbles. In many 
respects these views are of a distinctly revolutionary 
type, and subversive of current theories. Especially 
is this the case with regard to striated pebbles, gener- 
ally held to be of glacial origin, but which, in the 
author’s opinion, are rather the result of ‘“subter- 
ranean denudation,’ as exemplified by formations in 
the Vosges and elsewhere. It is remarked that these 
polished and striated fragments are almost exclusively 
calcareous, and that the scratches have been made by 
quartzitic and other hard rocks. A portion of surface- 
water, it is observed, sinks into porous soil, where 
subterranean denudation brings these slowly moving 
quartz-fragments into contact with irregularly shaped 
débris of calcareous rocks, which are eventually 
ground down into the polished and striated pebbles 
hitherto regarded as affording decisive evidence of 
glacial action. 
Tue replacement of limestone by hamatite, so as 
to produce masses or beds of iron ore, has been long 
recognised. In a paper on the genesis of certain 
Palzeozoic interbedded iron ore deposits, Mr. R. B. 
Earle makes a strong case for the similar replace- 
ment of sandstone by percolating ferruginous waters 
charged with carbon dioxide (Annals N. York Acad. 
Sci., vol. xxiv., p: 115). He uses the word “iron” 
freely in place of ‘iron oxide’’; but we gather that 


formation that flanks the Appalachian Mountains in-. 
cludes oolitic iron ores, in which the nuclei of the 
oolitic grains consist of partly corroded sand-grains. 
The quartz can be seen in microscopic sections to be 
in various stages of discoloration and replacement. 
The crusts of ore finally protect the nucleus from com- 
plete decay. The removal of quartz from granite and 
its replacement by calcite has been noted in the north 
of Ireland; but a better parallel with the Clinton 
occurrences is to be found in the Karroo sandstones 
of the Orange Free State, as described by Prof. R. B. 
Young (Trans. Geol. Soc. S. Africa, vol. xvii., 1914, 
p- 55). Here nodules of pyrite have originated, in 
which the iron sulphide “is seen not only to fill the 
interstices between sand-grains, but also to replace 
the latter to a considerable extent, the metasomatic 
action being most intense as the centres of the nodules 
are approached.”’ Felspar as well as quartz has been 
attacked in this case. 
Tue Transactions of the Naturalists’ Society of 
Kazan University contain several articles on the 
botany of western Siberia and the Steppes—‘‘In the 
Mountains and Valleys of the Altai’’ (vol. xlvi., No. 1), 
and ‘Researches into the Botanical Geography of 
Saissan in Semipalatinsk”’ (vol. xliv., No. 5), by V. A. 
Keller, and ‘‘ Botanical and Geographical Investiga- 
tions in Semipalatinsk”’’ (vol. xlv., No. 3), by V. 
Kriiger. Both authors give lists of the plants col- 
lected, with details of the localities where they were 
found and their environment. They also paid close 
attention to the temperature of the soil during the 
summer months when they were at work. Mr. Keller 
found the absolutely lowest soil temperature in the 
Altai in the upper part of the forest zone, and this 
zone seems to be in general colder than the mountain 
tundra which lies at a higher elevation. In the latter 
region the soil was considerably warmer where lichens 
abounded than in the tundra of bushes and mosses. 
The absolutely lowest temperatures (34°3° down to 
freezing point) were found in July in the section of 
the forest zone, where the vegetation was of a char- 
acter intermediate between those of sphagnum peat 
swamp and wet mossy forest. The highest tempera- 
ture (70°5°) occurred in the stony section of the moun- 
tain steppe. Mr. Kriiger also ascertained the propor- 
tion of moisture in the surface soil, and found that in 
the following six areas indicated by their predominant 
forms of vegetation—(1) Festuca sulcata, (2) Artemsia 
pauciflora, (3) Atriplex canum, (4) Obione verrucifera, 
(5) Halicnemum strobilaceum, (6) Salicornea herbacea 
—the percentage increased from (1) to (6). At about 
a foot below the surface the proportion also increased, 
but in a smaller ratio. The salinity of the soil was 
also smallest in the first and largest in the sixth area. 
Discussions of the anemographic observations re- 
corded at Port Blair and at Dhubri by Mr. W. A. 
Harwood are given in the Memoirs of the Indian 
Meteorological Depaitment, vol. xix. In an intro- 
duction, Dr. G. T. Walker explains that the analysis 
of the winds at Port Blair was almost completed by 
Sir John Eliot prior to his death. The Port Blair 
discussion, which embraces the observations for ten 
the ore referred to is usually hematite. The Clinton | years, September, 1894, to August, 1904, is of special 
NO. 2373, VOL. 95| 
