130 
NATURE 
[JuNE 8, 1899 
introduction of useful mechanical inventions, and the means 
were to be courses of philosophical lectures and experiments 
illustrating the applications of science to daily life. 
The Chairman, in acknowledgment of the toast, said that it 
was a great honour that so many eminent representatives of 
foreign science had honoured with their presence the centenary 
of the Institution. It was just 100 years ago when the Institu- 
tion entered upon its present premises. A long roll of names 
had lent lustre to their labours. Davy, Faraday, Young, 
Tyndall—above all, they should remember their founder, 
Benjamin Thomson, Count Rumford, whom it was easy to 
criticise, but whose virtues had been productive of great results. 
The work of the Institution had been in large measure the 
carrying out of Count Rumford’s ideas. It was said that he 
intended an institution of a more practical or industrial char- 
acter than the Institution now was. But changes had taken 
place. Facilities for communicating new discoveries were 100 
years ago few; competition was less keen; there was then 
much dislike of innovation, and there was extreme jealousy 
with the working classes of any reduction of manual labour. 
It was thus necessary to popularise discoveries ; and that was 
the aim of their founder. But now every such discovery was 
soon heralded to the public. Popular magazines had now 
articles on the manufacture of liquid air and other subjects of an 
abstruse character. Towards this wide diffusion of science the 
Royal Institution had largely contributed. Their principal 
objects were research, for which their laboratories gave 
ample means, and in respect of which special gratitude was due 
to Dr. Mond for his noble gift, and to Mr. Spottiswoode for 
his collection. The second object was to bring the results 
of research to the knowledge of those who could appre- 
ciate them, and these results were expounded in the 
evening lectures of the Institution. Thirdly, this knowledge 
was popularised by the afternoon lectures; and, finally, the 
rising generation were stimulated by the juvenile lectures to 
those who, it was hoped, were destined to take their part in 
future scientific investigation. 
On Tuesday afternoon a commemoration lecture was 
delivered at the Institution by Lord Rayleigh, the Prince 
of Wales being present. 
In the course of his remarks, Lord Rayleigh is reported by 
the Zzmes to have said that though his was intended to be a 
commemorative lecture, the idea of commemorating all the 
work that had been done at the Royal Institution was hopeless. 
Remembering that on other occasions he had spoken of the 
achievements of Faraday and Tyndall, he thought on this 
occasion he would do well to go still further back in the cen- 
tury and speak of Dr. Thomas Young, one of the earliest 
professors of the Institution. Young occupied a very high 
place in the estimation of men of science—higher, indeed, now 
than at the time when he did his work. Tis ‘* Lectures on 
Natural Philosophy,” containing the substance of courses 
delivered in the Institution, was a very remarkable book, which 
was not known as widely as it ought to be. Its expositions in 
some branches were unexcelled even now, and it contained 
some things which, so far as he knew, were not to be found 
elsewhere. The earlier lectures dealt with mechanics, and the 
reader would find as sound an exposition of that science as 
could be imagined. Elastic resilience, or what we should now 
call potential energy, was better dealt with there than in any 
other treatise he knew, for Young discussed the subject with 
cemarkable ingenuity, showing that the phenomena exhibited by 
two bodies coming into collision were comprehended under two 
cases. In the province of sound, Young was the originator of 
many of the most important principles on which the doctrine was 
now expounded, but it was with optics that his name was most 
closely associated, for Fresnel and he were the builders of the 
great structure of the undulatory theory. Lord Rayleigh then 
mentioned some of the points in which Young’s good work had 
been overlooked. In Young’s time one question of discussion 
was the change of the focus of the eye for varying distances. 
One suggested explanation, that accommodation was affected 
by an alteration in the external convexity of the eye, Young 
proved to be wrong by drowning his eye in water. This 
virtually altered the convexity, yet the power of accommoda- 
tion remained, and he therefore concluded it was due 
to a muscular alteration in the internal lens of the eye. 
Young was singularly successful in the theory of cohesion and 
NO. 1545, VOL. 60] 
capillarity, in which some of his earliest work was done, and 
he was the first to deduce an estimate of molecular dimensions 
from data afforded by that theory. The size of the molecule, 
according to his calculations, was not very different from that 
admitted at the present day. In the theory of the tides he 
made great advances, while his views on heat were very inter- 
esting, since he had the utmost contempt for the idea prevalent 
in his time that it was a separate entity, and expressed the hope 
that in time philosophers might arrive at a true conception of 
its nature as motion. Speaking of work which had been done 
at the Institution by men who held no regular appointment in 
it, the lecturer noted that Wedgwood, in conjunction with Davy, 
was the first to produce anything that could be called a photo- 
graph, while instantaneous photography, such as was required 
for rapidly moving objects, was carried out for the first time by 
Fox Talbot in the laboratory of the Institution. 
Another commemoration lecture is to be delivered 
as we go to press. Upon the invitation of the teachers 
of natural science in Oxford University, honorary 
members of the Institution will visit the University 
to-day. 
The principal historical apparatus in the Institution 
has been on view during the centenary celebration. 
An interesting souvenir of the centenary is an illustrated 
brochure referring to William Spottiswoode, and to his 
collection of physical apparatus just presented to the 
Institution by his son, Mr. W. H. Spottiswoode. The 
souvenir includes a memoir of Spottiswoode, reprinted 
from NATURE of April 26, 1883; a list of lectures 
delivered by him at the Royal Institution, notes on some 
of the more important objects in the collection of 
apparatus, a reprint of a paper by Spottiswoode on 
the laboratories of the Institution, and a chronological 
list of original work developed at the Institution. A 
photogravure of Spottiswoode, and a number of brilliant 
half-tone pictures of sets of objects in the collection 
of apparatus, form part of Mr. Spottiswoode’s interesting 
pamphlet. 
THE HEIGHT OF THE AURORA? 
GOOD story used to be told some years ago of 
a candidate, who, when undergoing the torture of a 
viva voce examination, was unable to reply satisfactorily 
to any of the questions asked. “Come, sir,” said the 
examiner, with the air of a man asking the simplest ques- 
tion, “explain to me the cause of the aurora borealis.” 
‘“* Sir,” said the unhappy aspirant for physical honours, 
“T could have explained it perfectly yesterday, but 
nervousness has, I think, made me lose my memory.” 
“This is very unfortunate,” said the examiner, “ you are 
the only man who could have explained this mystery, and 
you have forgotten it.” One is not prepared to say that 
exact and complete knowledge of the cause of this curious 
phenomenon has greatly advanced since the time when 
the examiner made this crushing rejoinder, and it is there- 
fore fortunate to have to treat of only one of the diffi- 
culties with which the whole problem is beset—the 
height at which the light manifests itself, or the limits of 
altitude above the earth’s surface at which it may be seen. 
But a preliminary difficulty arises in connection with 
even this bare statement. Is the aurora borealis a 
localised phenomenon? Has it a habitation as well as a 
name? Oris it, like the rainbow, an optical exhibition 
resulting from the operation of certain physical causes. 
In the case of the rainbow, the causes admit of a tolerably 
simple explanation, and little is to be learnt from the 
study of its general features as seen in the sky ; certainly 
we should not think it betokened any great show of 
wisdom to attempt to determine its height by any method 
of measurement or triangulation. The angular altitude 
is settled for us in a quite different manner, and it may 
1‘*The Altitude of the Aurora above the Earth's Surface.” By Prof. 
Cleveland Abbe. (‘‘ Terrestrial Magnetism,” vol. iit, 1898. 
