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“gravity as at zero. This contraction M. Spring thinks probably 
due to transformation of vesicular into octahedral sulphur ! 
In another paper to the Belgian Academy (Az//. No. 8) M,. 
Spring concludes that there is a relation between the dilatation 
and the atomic weight of simple substances ; for certain of them, 
as sulphur, selenium, and tellurium, nickel and cobalt, iron and 
aluminium, the former is inversely proportional to the latter. 
Otherwise expressed, the dilatation per atom (in the groups 
specified) is constant. The possibility is thus suggested of deter- 
mining the number of atoms contained in a molecule of a solid 
substance, » M. Spring is investigating this. 
Pror. W. HOLTz, inventor of the well-known Holtz electrical 
machine, has recently studied the various possible ways of 
arranging the inductors and armatures of his machine, This 
research was undertaken with a view partly to investigate the 
action of the analogous machine of Topler, in which the fixed 
plate is not pierced as in the Holtz machine, and partly to ascer- 
tain the reasons for the shifling brushes of light to be observed 
in the ordinary Holtz machine. The research, which is too 
lengthy to reproduce here, led to the conclusion that there is an 
advantage in the apertures of the fixed plate. 
To charge the electrodes of a secondary battery to their maxi- 
mum potential requires a quantity of electricity roughly propor- 
tional to their surface. But if the source from whence the 
charge is derived is of an electrometive force inferior to this 
maximum, then the polarisation-charge is limited, not by the 
surface of the electrodes merely, but by the fact that the oppos- 
ing polarisation completely stops the current. M. Blondlot has 
lately determined the quantities of charge required to polarise 
to such a limit a voltameter of given electrodes, when the elec- 
tromotive forces are also of given magnitude. This was done 
by using a voltameter with very small electrodes, and including 
in the circuit with it a battery, a ballistic galvanometer, and an 
apparatus for closing circuit during a determinate fraction of a 
second. By the device of increasing the area of one or other 
of the electrodes, M. Blondlot was able to study independently 
the two cases of polarisation by oxygen and of polarisation by 
hydrogen. The author further shows (Fournal de Physique) 
that the elementary capacity of an electrode for a given 
electromotive force does not depend on the nature of the 
electrode. The latter is also proved by a single qualitative 
experiment. It follows that to charge, by an instantaneous 
polarisation, the electromotive force between an electrede and 
electrolyte of value ¢, to a value ¢,, the same quantity of elec- 
tricity is always required, whatever the chemical nature of the 
electrolyte. Further, the charge of the double electrie layer at 
the surface of contact of an electrode and electrolyte does not 
depend on the nature of the electrolyte if the electric difference 
remains the same. M. Blondlot has also given an absolute 
measure of the initial capacity of platinum in water acidulated 
by sulphuric acid, and shows that this capacity may vary under 
different influences. 
GEOGRAPHICAL NOTES 
THE Journal of the Geographical Society of Tokio for the 
year 1851 has just been published. It is printed wholly in the 
Japanese character, and its contents are therefore inaccessible to 
all but a very few European readers, Besides reports of the 
meetings, and some other official information, it contains a paper 
on Saghalin and the Kurile Islands, and one on the historical 
geography of Japan. Some Japanese who have travelled in 
China have formed themselves into a society for publishing a 
topographical description of that country. This will contain 
little that will be new to English readers, as no Japanese has, 
we believe, penetrated into Central Asia from the side of China. 
The Japanese have given us much new information respecting 
Corea, but they have as yet added little else to our geographical 
knowledge. 
Mr. E. C. Hore’s paper on Lake Tanganyika forms the 
staple of the January issue of the Geographical Society’s Pyo- 
ceedings. The two maps which Mr, Hore furnishes are a valuable 
addition to the cartography of the lake, which is now for the 
first time delineated with any pretence to accuracy as a whole. 
The map of the southern part of the lake, Livingstone’s Lake 
Liemba, is on the scale of five geographical miles to the inch. 
Mr, Markham’s paper on the Y¥eannette expedition and Commo- 
dore Jansen’s notes on recent Dutch Arctic voyages, and Mr, 
Leigh Smith’s probable position we have already referred to at 
some length, and in connection therewith need only add that a 
map is now given of Wrangel Island from Lieut. Berry's survey. 
The geographical notes bring us some interesting news of African 
exploration, chiefly on the east side of the continent, and hold 
out the hope of a future paper on the little-known interior of 
Mozambique by a new traveller. 
THE first seven sheets of the Jarge map of Eastern Equatorial 
Africa, with the preparation of which Mr. Ravenstein was 
entrusted in 1878 by the Council of the Geographical Society, 
are at last ready for issue by Mr. Stanford. 
Dr. HARMAND, who has for some time been an assistant 
secretary of the French Geographical Society, and has latel 
been appointed Consul for France at Bangkok, is shortly to avail 
himself of the opportunity thus offered for making natural history 
and ethnographical collections in the Indo-Chinese peninsula. 
WE have received parts 27-29 of the new edition of Stieler s 
Hand Atlas, containing the following maps :—A railway and 
steamer map of Germany and neighbouring countries; Austria- 
Hungary ; India and Inner Asia, northern sheet ; a meteoro- 
logical chart of the world; Iran and Turan; general map of 
South America ; sheet 4 of the six-sheet map of South America ; 
North-East Africa and America ; South Africa and Madagascar, 
Other three parts, containing eight maps, will conclude the new 
issue of this Standard Atlas, which will have ninety-five maps 
in all. 
THE Deutsche Geographische Blatter (Heft 4 Band 10) of the 
Bremen Society contains the narrative of the brothers Krause, 
sent by the Society to explore the Behring Straits region, 
mainly for commercial purposes. Capt. Koldeway contri- 
butes a paper on the position of the Arctic ice during the past 
summer, which was peculiar in some respects ; Capt. Koldeway 
shows that it was dependent on meteorological conditions with 
which we are imperfectly acquainted, but for a knowledge of 
which the Arctic observing stations ought to do much. There 
is also a useful summary of the Arctic work of the year, in which 
it is claimed for Capt. Dallmann that he was the first to land on 
Wrangel Land in 1866. In a note on p. 448 of the ‘‘ Voyage 
of the Vega,” vol. i., Baron Nordenskjold, however, thinks it 
strange that Dallmann should only now have mentioned this 
voyage. : 
Srnce 1873, Herr Dietrich Reimer of Berlin has published at 
intervals important contributions to the literature of African ex- 
ploration, under the title of ‘‘ Beitrige zur Entdeckungsgeschichte 
Afrika’s.” The first issue was a series of small maps showing 
the progress of a general knowledge of Africa from antiquity 
down to the nineteenth century, The second contains a paper 
onthe part taken by Germany in African exploration, and a 
map, with text, showing what the various nationalities have done 
for African exploration during the nineteenth century. The 
third issue is a volume containing the journal of Dr. Paul Pogge 
during his exploration of the Lunda States, in the southern basin 
of the Congo in 1875-6. The fourth volume gives a narrative 
of Herr Otto H. Schiitt’s exploration on the Lower Quanza in 
1877-9. These are all of considerable value, especially the two 
last issues, which contain the results of much detailed work by 
competent scientific observers, We trust Herr Reimer will be 
encouraged to continue his enterprise. 
Tue Vienna Geographical Society celebrated the twenty-fifth 
anniversary of its foundation on December 22 last. The Society 
numbers 74 honorary and 644 ordinary Members ; its library 
consists of nearly 11,000 works. 
THE geographical weekly Das Ausland has changed hands. 
Up to December 31 last its editor was the well-known 
geographer, Fr. von Hellwald ; his place is now taken by Prof. 
Friedr. Ratzel of Munich. The paper will in future confine its 
contents solely to geographical and ethnographical subjects. 
ACTION OF FREE MOLECULES ON RADIANT 
HEAT, AND ITS CONVERSION THEREBY 
INTO SOUND* 
THE lecture opens with a brief reference to the researches of 
Leslie, Rumford, and Melloni, The labours of Tyndall 
and Magnus, as far as they bear upon the present subject, are 
then succinctly sketched, their points of difference being 
* Abstract of the Bakerian Lecture, by J. Tyndall, F.R.S., given at the 
Royal Society, November 24, 188r. 
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