a 
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January 29, 1914] 
Tue legislation which has been adopted in Ceylon 
against the diseases and pests of cultivated plants is 
the subject of a special Bulletin (No. 6) by the Ceylon 
Department of Agriculture. The bulletin, drawn up 
by Mr. T. Petch, brings together in a convenient 
form the regulations as to both internal and import 
legislation. The latter was commenced in igo. 
Under the regulations now in force all living plants, 
bulbs, &c. (except such as are imported for consump- 
tion), also oranges and other fruits of the Citrus 
family, and cotton seed, are subjected to fumigation 
with hydrocyanic acid, whilst the seed of tea is fumi- 
gated with formalin vapour. The importation of 
cacao plants from the Dutch East Indies, and pepper 
plants from India is totally prohibited. Internal legis- 
lation was not introduced until some years later, and 
only after it had been fully discussed with all the 
interested parties. It was first applied to the coconut 
beetles in 1907, but it is now extended to the shot-hole 
borer (Xyleborus fornicatus), Hevea canker, and the 
stem bleeding-disease of coconut. 
WE have received a reprint of the article on plant 
ecoloey (**Oekologische Pflanzengeographie”’) contri- 
buted by Dr. E. Riibel to the ‘‘ Handwérterbuch der 
Naturwissenschaften’’ now being issued by Gustav 
Fischer, Jena. In this article, which is practically a 
text-book of the subject, the author deals concisely 
with the various factors of the environment which 
determine the characters of the various types of plant 
community, and after reviewing the various systems 
of classification of these communities which have been 
proposed, sets out in detail the classification recently 
suggested by himself and Dr. Brockmann-Jerosch. 
In this scheme, plant communities are primarily 
divided into four types, composed respectively of 
woody plants, of herbaceous plants on relatively rich 
soil (meadows in the widest sense), of herbaceous 
plants on poor soil (deserts in the widest sense), and 
of free-floating aquatic plants (phytoplankton). The 
geographical distribution and biological characters of 
each type are given, and the author has compressed 
into fifty papers a remarkable amount of information, 
besides indicating the rapid progress which has been 
made in recent years in this branch of botany, and 
indicating the more important recent literature of the 
subject. 
In the second part of the Verh. Naturhist. Vereins 
d. preuss. Rheinlande u. Westfaliens for 1912 (1913) 
Dr. W. Gothan records the discovery in the neigh- 
bourhood of Dortmund, in the Ruhr basin, of a bed 
containing number of well-preserved Carboniferous 
ferns. They are of interest not only as_ being 
the first obtained from this locality, but from the 
fact that they include a new species, and also from a 
distributional point of view. The article is illustrated 
with three plates. 
Dr. Fettx Oswatp, whose hand-printed work on 
the geology of Armenia was reviewed in Nature in 
1906 (vol, Ixxv., p. 197), has rendered his results more 
accessible by contributing the section on ‘‘ Armenien ”’ 
to the “Handbuch der regionalen Geologie,” edited” 
by Profs. Steinmann and Wilckens. This is illus- 
NO. 2309, VOL. 92] 
NATURE 
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i 
615 
trated by a tectonic and a geological map, and by 
sections (Heidelberg : C. Winter; price 2.80 marks). 
The author points out the rise of a large part of the 
region above the sea in late Jurassic times; the two 
types of marine Cenomanian strata, separated by a 
gneissic ridge south of Tiflis into an eastern and a 
western basin; and the folding of marine Miocene 
strata during the Alpine movements in the Tortonian 
epoch. 
In the Atti dei Lincei, vol. xxii. (2) 5, Prof. T. 
Levi Civita discusses the conditions that must be 
satisfied by a function in order that it may have an 
addition-theorem in which a function of x+y is 
represented as the sum of products of functions of x 
and of y respectively. The ordinary exponential and 
circular functions afford illustrations of this property. 
AccorpinG to Torricelli’s theorem the velocity of 
efflux of a liquid from a small aperture in steady 
motion is equal to the velocity acquired by falling 
from the height of the liquid surface. From a note 
published in the Comptes rendus (vol. clvii., p. 48) by 
Prof. T. Levi Civita, it would appear that the same 
result holds good for the initial velocity of efflux 
when an opening is suddenly made in the walls of the 
containing vessel the liquid being previously at rest. 
It appears probable that this result could be easily 
tested experimentally. 
No. 2 of the Jahrbuch der Drahtlosen Telegraphie 
contains an article by F. Kiebitz on the refraction of 
electric waves in the atmosphere. Since the upper 
strata have a smaller density, luminous and electric 
waves are propagated more rapidly high above the 
ground than near the surface. This would lead to a 
bending forward of the wave-front, were it not for 
the curvature of the earth. The question now arises 
whether this curvature is sufficient to counteract the 
“prism effect’’ of the air. The author studies this 
question numerically, and finds that, to counteract 
the curvature, the densities on the ground and 1 km. 
above it should be in the ratio of 29:13. The actual 
ratio for dry air is 29:26, and for moist air about 10 
per cent. greater. So far from bending forward, 
therefore, the waves will lean backward and be de- 
flected into the upper atmosphere. There they en- 
counter the conducting layer, and are reflected down- 
wards, but only it the lower surface of this conducting 
layer is fairly uniform. Any folding or interruption 
of this surface will (as pointed out by Sir Oliver 
Lodge) lead to a reflection towards the origin or a 
dissipation into still higher strata. Such disturbances 
of uniformity must occur wherever there are irregular 
variations of temperature and moisture, more par- 
ticularly over land areas. It is found indeed that 
sunshine on land has a deleterious effect on the clear- 
ness of wireless signalling. Ideal conditions would 
be presented by air saturated with moisture, together 
|, witht a_ uniformly stratified distribution of tempera- 
ture. The best. conditions are presented in this respect 
by the Pacific Ocean, where we may expect to attain 
the maximum ranges of signalling. 
A HANDSOME clockwork orrery has just ‘been com- 
pleted by Messrs. G. Philip and Son, Ltd., 32 Fleet 
Street, and we have had the opportunity of examining 
