May 25, 1899] 
NATURE 
87 
the African Continent, to be entitled ‘‘The Fauna of South 
Africa,’ which will be published by Mr. R. H. Porter. The 
first volume, by Mr. Arthur C. Stark, containing Part i. of the 
birds, will shortly appear ; and the second volume on the mam- 
mals, by Mr. W. L. Sclater, is in a forward state. The volumes 
will be of octavo size, and will be illustrated by numerous wood- 
cuts in the text. 
FroM the Gazette of British Central Africa we are pleased to 
learn that the Administrator of Northern Rhodesia has _pro- 
claimed the large district known as the ‘‘ Mweru Marsh,” lying 
on the east side of the lake of that name, as a ‘‘ game preserve,” 
in which no game-animals are allowed to be shot without special 
licence. This excellent step will, we trust, tend largely to the 
preservation of the existence of the elephants and other large 
mammals frequenting that district, which has lately received 
rather too frequent visits from British sportsmen. The Mweru 
swamps will be found fully described by Mr. Croad in the 
Geographical Journal for June 1898. He says the elephant- 
hunting there is as good as any south of the equator. 
WE have received from Herr B. Walter a reprint of his paper 
on the nature of electric sparks, published in Wredemann’s 
Annalen, 66. The method of investigation adopted consisted 
in photographing the sparks’ produced by an induction-apparatus 
on a moving plate. The diagrams thus obtained under various 
conditicns bear some resemblance to photographs of so-called 
“ribbon lightning,” and show that the electric spark does not 
consist of a single discharge alone, but of a succession of brush 
discharges each following in the path of the previous one. In 
one case, the interval between successive discharges was found 
to be roughly the ten-thousandth of a second. 
Prors. ELSTER AND GEITEL have sent us two papers dealing 
with their investigations on the nature of Becquerel rays. The 
experiments appear to negative the view that the source of energy 
of these rays is to be attributed to other radiations falling on the 
uranium salts which emit them, and Sir William Crookes’ 
hypothesis that the energy is perhaps derived from the air, 
seems rendered doubtful by experiments made with uranium 
salts 7 vacuo. The authors confirm the discovery by M. and 
Mme. Curie of certain substances derivable from the uranium 
pitch of Joachimsthal, in Bohemia, possessing the property of 
emitting these rays in a high degree. 
A SIMPLE verification of the principle of Archimedes for 
gases is described by M. P. Métral in the Journal de Physique 
for April. Two flasks, each of 1 litre capacity, are suspended 
from the scale pan of a balance. On placing the lower one ina 
vessel filled with carbon dioxide, the equilibrium is destroyed, 
but is restored again on filling the upper one with the same gas. 
To verify the principle for gases lighter than air, the two equal 
vessels are attached neck downwards by clamps to a horizontal 
beam suspended from the scale pan of a balance. On lowering 
an inverted jar of hydrogen over one vessel, equilibrium is 
broken, but is restored by filling the second vessel with 
hydrogen. 
THE energy of Roéntgen rays has been investigated by the 
Rev. Alexander Moffat by measuring the luminous energy given 
out by a fluorescent screen when exposed to the rays. This 
energy is of course very small, but it must be remembered that 
it only represents 4 per cent. of the energy impinging upon the 
screen, and also that the interval between two successive X-ray | 
discharges is about 1000 times the period of time covered by the 
discharge itself. Allowing for these facts, it appears that if the 
Rontgen rays were continuous instead of intermittent, they 
would exert an effect 500 times greater than sunlight when 
falling perpendicularly upon a surface. 
NO. 1543, VOL. 60] 
CoHERERS made of platinum or gold filings du not “‘ de- 
cohere” on shaking them up after the electric waves have 
ceased. The more oxidisable metals do. But as M. A. 
Blondel pointed out at a recent meeting of the Societe Frangaise 
de Physique, the greatest sensitiveness is attained when the 
metal is only moderately oxidisable, and good results are ob- 
tained with alloys of silver and copper artificially oxidised to a 
degree which can be easily recognised by the change of tint. 
AN interesting and timely paper on milk as a food article ap- 
pears in Zszs. It is written by Dr. Schlossmann, and deals with 
the composition and properties of human and animal milk, and 
with the means for ensuring a proper supply of what is, with 
bread, the cheapest and most indispensable of food-stuffs. The 
adulteration of milk by water may be detected by the presence 
of nitric acid, which is never contained in undiluted milk. The 
number of dairies containing only healthy milch cows is very 
small indeed, but most of the danger may be averted by heating 
the milk to near boiling point, or by freezing it. One firm 
near Dresden adds quantities of milk ice to every consignment 
to keep it cool. 
A NEW family of Paleozoic corals is introduced under the 
name Monzloporidae, by Mr. Amadeus W. Grabau (Proc. Boston 
Soc. Nat. Hist., April 1899). In this new family it is proposed 
to include the genera Monz/ifova and Ceratopora, forms found 
in Devonian and Lower Carboniferous strata. The genus 
Monilipora was established twenty years ago by the late Prof. 
Nicholson and Mr. R. Etheridge, jun. Cerafopora is now 
described by Mr. Grabau ; it appears earlier in time than the 
other genus, and is less specialised in structure. 
Mr. Lawrence M. LAMBE publishes a series of notes on 
Canadian Paleozoic corals (Ottawa Naturalist, February and 
March 1899). Tle calls attention to certain structural details 
which had previously been overlooked or misinterpreted, and he 
describes one new species of Lithostrotion. 
WE have just received vol. iv., No. 3, of ‘‘ Indian Museum 
Notes,” containing, zz¢er a/éa, an article by Mr. F. Finn, the 
Deputy-Superintendent of the Museum, calling attention to the 
abundance of small green Homoptera (locally known as “‘ green 
bugs”’) in India, and suggesting that they might be imported 
into England as food for cage-birds, There seems, however, to 
be some difference of opinion among the bird-fanciers who have 
experimented with them as to their value; but this may be due 
to their being more relished by some kind of birds than by 
others. 
Bulletin No. 19 (new series), U.S. Department of Ento- 
mology, ‘‘Some insects injurious to garden and orchard crops, 
prepared under the direction of the Entomologist, by F. H. 
Chittenden, Assistant Entomologist,” relates chiefly to Coleoptera 
(flea-beetles, chafers, bark-beetles, ladybirds, &c.), Homoptera, 
and Lepidoptera. Special attention is called to the squash 
ladybird (Zpz/achna borealis, Fab.) and the squash bugs (dasa 
tristis, De Geer, and A. armigera, Say), and to the recently 
introduced moth (Hedila wndalis, Fab.), a South European 
species, which has lately been committing serious ravages on 
cabbage, turnip, and other cruciferous plants in the neighbour- 
hood of Augusta, Georgia. 
A DESCRIPTIVE list of recent large scale maps, including both 
surveys and compilations, together with a list of some large 
atlases, has been prepared in the Intelligence Division of the 
War Office by Mr. Alexander Knox, Map Curator, and can be 
obtained from Messrs. Eyre and Spottiswoode. The volume 
forms a supplement to ‘‘ Notes on the Government Surveys of 
the Principal Countries of the World.” 
