118 
exchange signals with Lieut.-Commander Green over my over- 
land leenain and, in conjunction with Messrs. Ellery and 
Russell, make fresh determinations of the difference of longitude 
between Adelaide, Melbourne, and Sydney.” 
Since our last anniversary, Sir George Airy, the late Astro- 
nomer Royal, having completed his eightieth year, and nearly 
half a century of office, has retired. Of his services to science, 
and to this Society as President, and in other ways, the time to 
speak has happily not yet arrived. His great intellectual powers 
are in fact in no way impaired, and so far from having brought 
his period of activity to a close, he hopes to employ his well- 
earned leisure in completing a favourite work, the Numerical 
Lunar Theory. 
His successor, Mr. Christie, from his long experience in the 
Royal Observatory, will combine a thorough training in the 
remarkable organisation and methodical administration for 
which his predecessor was so conspicuous, with the full vigour 
of life, and an active interest in the more modern developments 
of astronomy, in which he is already distinguished. 
The future of the Royal Observatory is a subject on which 
the mind of Sir George Airy often exercised itself, and to which 
he alluded more than once in his Reports to the Board of 
Visitors. With bis fundamental proposition that observational 
astronomy, in its bearing on the improvement of navigation, 
must always be its main line of work, every one must agree. 
Over and above this, the expressed wish of the Board of Visitors, 
and the practice of the last few years, have already sanctioned 
the addition to the ancient duties of the Observatory of some 
of those long and systematic series of observations, such as 
that of the solar protuberances, and the motion of the fixed stars 
in the line of sight as shown by the spectroscope, which are 
beyond the scope of an amateur, and above the power of any 
individual astronomer, however devoted to his work, to per- 
manently maintain. How far it may be desirable to continue 
magnetic and meteorological observations beyord the necessities 
of an astronomical observatory, are questions which will doubt- 
less engage the attention of the present director. The main 
question must be, What distribution of these branches of study 
among Greenwich, Kew, and other establishments, will in the 
end best conduce to the progress of science? And with a view 
of giving full scope to the judgment and skill of the present and 
future holders of the office the Board of Admiralty have, as 
I understand, decided to consider a revision of the terms of the 
Royal Warrant under which the appointment is made. 
This year has been signalised by the meeting of a most impor- 
tant scientific congress—the International Congress of Electri- 
cians, held at Paris. The recent developments of the practical 
applications of electricity rendered the occasion favourable both 
for organising a special exhibition devoted solely to this branch 
of science, and also for assembling the electricians of all 
countries. 
The general purpose of this Congress was to discuss, and if 
possible to settle, some of the numerous difficulties which per- 
plex both the physicist in his studies and the constructor in his 
work, 
But chief among the subjects proposed to, and undertaken by, 
the Congress was that of fixing a system of electrical measures 
for international adoption. 
Perhaps in no subject is the necessity of uniform system of 
standards so striking as in electricity. This science, both in its 
practical applications, such as telegraphy, and in the great natural 
problews of terrestrial magnetism and atmospheric electricity, 
refuses to recognise any artificial divisions of the surface of the 
globe, whether ethnological or political. 1t rarely happens, in 
operati. ns undertaken on so large a scale as the study of electri- 
city and its industrial applications, that an opportunity presents 
itself of arranging for concerted and harmonious action through 
a period extending to a distant future. Before a branch of 
industry has attained sufficient importance to claim international 
recognition, it has usually gone through the process of consider- 
able development in different countries; and in each of these 
developments it has often received a stamp of local character 
which makes it difficult to reduce the whole to one uniform 
system. but in the case of electricity there were fortunately 
present special circumstances which facilitated the adoption of 
uniform standards, Foremost among these was the fact that the 
development of its practical applications, in other departments 
than telegraphy, were so recent that it was not too late to legis- 
late for it as though it were but just about to begin. Secondly, 
the international character of telegraphy, and the fact that the 
NATURE 
[Dee. 1, 1881 
manufacture of its apparatus had always been confined to the great 
centres of civilisation, had both tended to limit the number of 
existing systems of measurement, and prevented that multiplicity 
of standards which would certainly have arisen had such manu- 
facture been carried on in numerous and in isolated localities, 
But by far the most important influencing circumstance was the 
happy idea due to the British Association of adopting standards 
based on absolute measures. The Association did not allow the 
idea to remain barren; but, through the instrumentality of its 
Committee on Electrical Standards, it gave to the world the 
admirable units of the Ohm, the Volt, and the now re-christened 
Weber ; and the eminent men who formed that Committee may 
now point with honourable satisfaction to the fact that the 
Electrical Congress decided unanimously to recommend for 
universal acceptance those units which that Committee so early 
adopted. 
With the single exception of the unit of current which, in 
order to avoid an ambiguity in the signification of Weber, re- 
ceives the title of Ampére, the names are left substantially with- 
out change. 
The adoption of these units for international use is to be pre- 
ceded by a new and more careful redetermination of the ohm at 
the hands of the great physicists of all nations. And it is in- 
tended that this redetermination shall result in a standard for 
general adoption. Thus electricity will be the first of the prac- 
tical sciences to be freed from all difficulties due to local stand- 
ards ; and it is to be hoped that this example may be followed 
in other sciences concerned with practical life. 
The following are the actual resolutions adopted by the Inter- 
aes Congress of Electricians at the sitting of September 22, 
1881 :— 
1. For electrical measurements, the fundamental units, the 
centimetre (for length), the gramme (for mass), and the second 
(for time), are adopted. 
2. The ohm and the volt (for practical measures of resistance 
and of electromotive force or potential) are to keep their existing 
definitions, 10% for the ohm, and 10% for the volt. 
3. The ohm is to be represented by a column of mercury of a 
square millimetre section at the temperature of zero Centigrade. 
4. An international commission is to be appointed to deter- 
mine, for practical purposes, by fresh experiments, the length of 
a column of mercury of a square millimetre section which is to 
represent the ohm. 
5. The current produced by a Volt through an Obm is to be 
called an Ampére, 
6. The quantity of electricity given by an Ampére in a second 
is to be called a Coulomb. 
7. The capacity defined by the condition that a Coulomb 
charges it to the potential of a Volt is to be called a Farad. 
The remainder of the work of the Congress consisted mainly 
of the discussion of various interesting questions bearing upon 
electricity ; and although these did not in many cases issue in 
precise recommendations, yet they were not altogether devoid of 
practical results. The questions which chiefly attracted its atten- 
tion were those of terrestrial magnetism and earth-currents, 
atmospheric electricity, and the more practical but perplexing 
question of lightning conductors. In all these matters the need 
of close and continuous intercourse between the observers of 
different nations was strongly felt ; and the Congress passed 
resolutions recommending combined action both in the way of 
observations carried on simultaneously and with like apparatus, 
and also of frequent if not continuous telegraphic communica- 
tion of the results of these observations. The organisation of 
so extensive and perhaps so costly a system of combined obser- 
vations must depend to a great extent on the various Govern- 
ments, and also on the goodwill and generosity of the great 
telegraphic companies; but it is much to be wished, for the sake 
of science, that some progress in that direction may soon be 
effected. The present state and prospects of electro-physiology 
also received careful discussion, but the difficulties of the subject 
precluded any definite conclusions. The same was the case with 
the question of photometry as applied to the intense light with 
which electricity furnishes us, Resolutions recommending the 
adoption of certain provisional photometric standards were 
passed ; but these only evidenced the strong feeling that pre- 
vailed in the Congress, that some new departure must be made, 
and that a new standard of illumination (such as perhaps the 
glow of platinum on the point of fusion) must eventually be 
adopted for electric lights. 
I have described the more important of the results of the 
