April 6, 1882] 
NATURE 
539 
little volume (‘ A Year in Manitoba, 1880-81’) is published by 
Messrs. W. and R. Chambers, and contains a full and concise 
statement of the experience of an officer and his sons on a small 
farm which they took, about ten miles from Winnipeg. There 
were not a few hardships certainly, and these are clearly 
brought out ; but the other side is quite as clearly and fairly 
stated, with a considerable balance in its favour. For any one 
contemplating emigration to the Canadian North-west, this is the 
book to get. 
BrEsipes Mr. O’Neill’s paper on his three months’ journey 
inland from Mozambique, the April Proceedings of the Geo- 
graphical Society contain a résumé of the information just laid 
before Parliament on the subject of the Russo-Persian frontier 
east of the Caspian, accompanied by a map, which can only 
pretend to reproduce the Russian view of the question. The 
other paper describes the journey of a Russian officer from 
Geoktepeh to the Khivan oasis, and is a translation from 
the Russian. Perhaps the mos! notable matter in the geo- 
graphical news is the treaty which M. de Brazza imposed on the 
native chiefs at Stanley Pool, and by which they undertook to 
admit none but Frenchmen; some late news is also given re- 
specting Dr. Junker’s journey in Central Africa, and Mr. J. M. 
Schuver’s progress to the south-west of Abyssinia. We are 
glad to see, too, that the international polar meteorological 
expeditions are not neglec’ed, some very interesting information 
being furnished respecting those of the Danes to G=dshaab, in 
~ West Greenland, and of the Dutch to the mouth of the Yenissei, 
A note is also devoted to the recent Danish explorations at 
Mear, the Jacobshayn fjord. The French Geographical Society’s 
meetings are very fully reported, as, indeed, they generally are. 
A NEW Geographical Society was formed last month at 
Greifswald, in Pomerania. 
A CORRESPONDENT points out, in reference to Dr. Rae’s cor- 
rection of last week, that a gold medal was awarded to Nain 
Singh in 1877, as will be found by reference to the Journal for 
that year, or in the Proceedings (old series), vol. xxi. A gold watch 
bad previously been awarded to Nain Singh in 1868, for his 
route-survey from Lake Mansarowar to Lhasa. 
Mr. R. ARTHINGTON, of Leeds, who is well-known as the 
munificent benefactor of African mi sions, has just presented to 
the Baptist Society a further sum of rooo/, towards the cost of 
building a steamer for the Upper Congo. 
THE Constantine gold medal of the Russian Geographical 
Society was not awarded this year; the medal ot Count Liitke 
was awarded to Major-General Ernfeldt and Col. Lebedeff, for 
their geodetical and topographical work in the Balkan Penin- 
sula; the great gold medal of the Ethnographical Section was 
awarded to M. Potanin for his explorations in North-Western 
Mongolia; that of the Statistical Section to M. Romanoff for 
his work on emigration from the Government of Vya'ka. The 
small gold medals were awarded to the astronomer, F. F. 
Schwartz, the well known explorer of Eastern Siberia, for his 
determinations of | ositions in Turkestan and Central Asia; to 
M. Domojiroff, for anemometrical observations on board of 
ships; to M. Malakhoff, for ethnographical explorations on the 
Ural 3; and to M. Yadrintseff, for his work, ‘‘ Travels in Western 
Siberia and on the Altai.” Silver medals were awarded to 
Mydame L. Poltoratzkaya, for her album of photographs from 
Western Siberia; to M. Lakhmeyer, for photographs of Caucasus 
and Ural; to M. Kalitin, for maps of the route between Khiva 
and Akhal-Teke ; to M, Ivanoff, for explorations of the 
Zerafshan glacier ; to M. Agapitoff, for explorations of the black 
earth and loess, in the Government of Irkutsk ; to M. Roubach, 
for meteorological observations on the island of Oesel; to M. 
Zagursky, for his works on the Caucasian languages and his 
biography of the well-known explorer of these langnages, R. K. 
Uslar ; and to MM, Stevanovsky and Rudinsky, for collections 
of Russian songs. 
THE last number of the /zves/zz of the Russian Geographical 
Society contains, among other interesting materials, two lists of 
points whose latitudes and longitudes were determined by the 
indefatigable explorer of Eastern Siberia and Turkestan, F. F. 
Schwartz, the Dorpat astronomer, during the years 1879 and 
1880. After having determined, in 1879, the positions of ten 
points in Eastern Turkestan, he now publishes a list of twenty- 
four points in the Kulja territory, from Kulja along the two long 
valleys of the Kash and of the Kunghes rivers, which cross this 
territory from east to west, that of Kunghes having been ex- 
| mum in the opposite direction. The ordi- 
| nary currents witha contact breaker would 
plored to its source, and the most eastern point reached by M. 
Schwartz being the Narat Pass, at the south-eastern frontier of 
the Kulja territory. A series of determinations between Vernyi 
and the Narat Pass, along the Tekes river, were made during 
the same year. The numerous magne'ic observations made by 
M. Schwartz during these two journeys, will be published as 
soon as calculated. 
MATTER AND MAGNETO-ELECTRIC ACTION'* 
*HE late Prof. Clerk Maxwell, in his work on “‘ Electricity 
and Magnetism ” (vol. ii. p. 146), lays down as a principle 
that ‘‘ the mechanical force which urges a conductor carrying a 
current across the lines of magnetic force, acts, not on the 
electric current, but on the conductor which carries it. If the 
conductor be a rotating disk or a fluid it will move in obedience 
to this force, and this motion may or may not be accompanied 
with a change of position of the electric current which it 
carries. But if the current itself be free to choose any path 
through a fixed solid conductor or a network of wires, then, 
when a constant magnetic force is made to act on the system, 
the path of the current through the conductors is not permanently 
altered, but after certain transient phenomena, called induction 
currents, have subsided, the distribution of the current will be 
found to be the same as if no magnetic force were in action. 
The only force which acts on electric currents is electromotive 
force, which must be distinguished from the mechanical force 
which is the subject of this chapter.” 
In the investigation on electric discharges, on which Mr. 
Moulton and myself have been long engaged, we have met with 
some phenomena of which the principle above enunciated affords 
the best, if not the only, explanation. But whether they be 
r- garded as facts arising out of that investigation, or as experi- 
mental illustrations of a principle laid down by so great a master 
of the subject as Prof. Clerk Maxwell, I have ventured to hope 
that they may possess sufficient interest to form the subject of 
my present discourse. 
‘The experiments to which I refer, and of which I now pro- 
pose to offer a summary, depend largely upon a special methed 
of exciting an induction-coil. This method was described in 
two papers, published in the Philosophical Magazine (November, 
1879), and in the Proceedings of the Royal Society (vol. xxx. 
p. 173), respectively ; but as its use appears to be still mainly 
confined to my own laboratory, and to that of the Royal Institu- 
| tion, I will, with your permission, devote a short time to a 
description of it, and to an exhibition of its general effects. 
The method consists in connecting the primary circuit directly 
with a dynamo- or magneto-machine giving alternate currents. In 
the present case, I use one of M. de Meritens’ excellent machines 
driven by an Otto gas-engine. The speed of the de Meritens 
machine, so driven, is about 1100 revolutions per minute. 
In this arrangement the currents in the secondary are of course 
alternately in one direction and in the other, and equal in 
strength ; so that the discharge appears to the eye, during the 
working of the machine, to be the same at both terminals. 
The currents in the primary are also alternately in one direc- 
tion and in the other, and consequently, at each alternation, 
their value passes through zero. But they differ from those 
delivered in the primary coil with a direct current and contact 
breaker in an important particular, namely, that while the 
latter, at breaking, fall suddenly from their full strength to 
zero, and then recommence with equal suddenness, the former 
undergo a gradual although very rapid change from a maximum 
in one direction through zero to a maxi- poe ; 
Ls) ae 
| \ 
be represented by a figure of this kind, 
while those from the alternate machine approximately by a curve 
of the following form. The rise and fall 
of the latter are, however, sufficiently — oN @e 
rapid to induce currents of high tension LU US 2 
and of great quantity in the secondary. 
From these considerations it follows : first, that as the machine 
effects its own variations in the primary current, no contact 
breaker is necessary ; secondly, that as there is no sudden rup- 
ture of current, there is no tendency in the extra current to pro- 
duce a spark or any of the inconveniences due to an abrupt 
opening of the circuit, and consequently that the conden-er 
Lecture at the Royal Institution, Merch 37, by Dr. W. Spottiswoode, 
Pres.R S. 
