March 21, 1895] 



NATURE 



495 



of that (Fortnightly Rnie'M, November 1894), I must content 

 myself with trying to give you, in a few sentences, some idea of 

 the range of his intellect. 



His investigations on optics were not less important than 

 those on sound. lie invented the ophthalmoscope, by which 

 the oculist can study the inmost recesses of the eye. The 

 theory of colour vision, the theory of binocular vision, the 

 curious subjective effects which are produced when we de- 

 liberately deceive our own senses by the stereoscope ; these 

 subjects he made especially his own. 



In the field of mathematics he was the first to define the 

 peculiar rotatory motion of a liquid known as vortex-motion. 

 Great men had laid the foundations of hydrodynamics before 

 him, but all had overlooked the importance and laws of the 

 vortex. Since the memoir of Helmholtz was published the 

 subject has been widely studied. Lord Kelvin has originated 

 the famous vortex-ring theory of matter ; Prof. Fitzgerald has 

 suggested that the ether may be a complex of vortices, or, as it 

 has been called, a vorlex-sponge. 



On electricity he wrote much — on the theory of the galvanic 

 cell, on electrolysis, on electromagnetism. 



In England, at all events, we give the preference, as regards 

 the last subject, to the theory and writings of our own Max well. 



A lecture, or rather many lectures, might be delivered on 

 each of these topics, but I prefer to devote the few minutes 

 that remain to other subiects. 



As I have already said, von Helmholtz, in an age of special- 

 ists, was a universal genius. His intellect CDuld light on 

 nothing which it did not illuminate. Hence his opinions on 

 side issues are of more than ordinary importance, his "obiter 

 dicta" are worth attention, his popular lectures acquire a 

 special interest. Let us for a few moments turn to these. 



The watchword of Helmholtz in dealing with educational 

 problems is "freedom." Freedom for the student, freedom 

 for the teacher. 



In England we are fond of insisting that there are certain 

 things which everybody who aspires to academic rank must 

 know ; of hedging in our students by prescribed courses of 

 study. We make them feel that general culture is an iron- 

 bound safe, which they must wrench open before they can 

 attain the gem of real knowledge, rather than a setting, with- 

 out which the most profound acquirements seem unattractive 

 and dull. Yet von Helmholtz, one of the most highly educated 

 men, one of the most comprehensive geniuses of the latter end of 

 the century, will have no set courses, except as a preparation for 

 a definite profession, is proved that Germany has " retained the 

 old conception of students, as that of young men responsible to 

 themselves, striving after science of their own free will, to whom 

 it is left to arrange their own plan of studies as they think 

 best." Not content with having m.ade the attainment of this 

 ideal almost impossible for English students, doctrinaire educa- 

 tionalists are now beginning to thr')W their net around the 

 teacher. It is claimed that as the student must go through a 

 prescribed course of study in order to learn, so the teacher must 

 be drilled and examined before he is allowed to teach. What- 

 ever can be said f.jr this plan as regards the less advanced class 

 of teachers, who are to devote themselves to the instruction of 

 children — and in this case I believe there is something to be said 

 for it — it is quite opposed to von lielmholtz's view of wh.at is 

 best when the teaching is of university rank, and the students 

 are men and women. Make it easy for whoever has given some 

 proof of knowledge, and wants to teach, to try his hand ; make 

 it easy for the student to go to the teacher from whom he gains 

 the most. Look for the best educational results, not necessarily 

 from the best lecturer, but from the man who is in closest con- 

 tact with his subject. Do not force your teacher on his 

 audience, but do all you can to establish a bond of sympathy 

 between them. Trust, in a word, to the free play of living 

 forces, and not to the hampering restrictions of "necessary 

 subjects" and "compulsory lectures." This is a paraphrase of 

 the views which Helmholtz held, and he illustrated them by 

 the history of this Institution itself. 



"I have often," he said, "wondered that the Roy.al 

 Institution of London, a private society, which provides for its 

 members and others short courses of lectures on the progress of 

 natural science, should have been able to retain permanently 

 the services of men of such scientific importance as Humiihry 

 Davy and Faraday. It was no question of gi'eat emolument < ; 

 these men were manifestly attracted by a select public, con- 

 sisting of men and women of independent mental culture. ' And 

 then he goes on to show that in a German university the teacher 



NO. 1325, VOL. 51] 



is attracted to his work, because he has to deal with a body of 

 students, who are capable of forming opinions, and of judging 

 what is best for themselves. 



And this leads us to another point. Von Helmholtz insisted 

 that it is useless and dangerous to crowd the universities with 

 students, who are not capable of taking advantage of the oppor- 

 tunities they offer. " The majority of students," he says, " must 

 come to us with a sufficiently logically trained judgment, with 

 a sufficient habit of mental exertion, with a taste sufficiently 

 developed on the best mo lels to be able to discriminate truth 

 from the bubbling appearance of truth. ... It would be very 

 dangerous for the universities if large numbers of students 

 frequented them, who were less developed in [these] respects. 

 The general self-respect of the students must not be allowed to 

 sink. If that were the case, the dangers of academic freedom 

 would choke its blessings. It must, therefore, not be looked 

 upon as pedantry, or arrogance, if the universities are scrupu- 

 lous in the admission of students of a different style of educa- 

 tion. It would be still more dangerous if, for any extraneous 

 reasons, teachers were introduce t into the faculty, who have 

 not the complete qualifications of an independent academical 

 teacher." ("Popular Lectures," vol. ii. 1S81, p. 264-5.) 



It would be out of place on this occasion to attempt to apply 

 these views to existing circumstances in London; but with the 

 knowledge that the finil constitution of a Teaching University 

 for the metropolis may be decided within the next few months, 

 I cannot but feel that London will be happy if it escapes from 

 the fetters which some of its so-called friends are forging for 

 learning ; and if, on the other hand, the wise determination of 

 the Gresham Commissioners to include in the university only 

 institutions of university rank, can be maintained against the 

 attacks which will be made upon it. 



Lastly, I wish to defend the memory of von Helmholtz from 

 a possible misconception. Those who cultivate art may per- 

 haps look upon him as the poet or the master of style look 

 upon the grammarian, as a mere gerund-grinder, occupied with 

 the study of the dead materials wnich they alone can use. Of 

 course Helmholtz was not a great artist in the sense that he was 

 a great scientific man, but it would be most unfair to picture 

 him as interested only in the study of laws, and as insensitive to 

 beauty, as occupied with sound and light, but careless as to 

 music and painting. I could quote passage after passage from 

 his works to prove his keen sense of the loveliness as well as of 

 the order of nature, to show the homage that he paid, and the 

 freedom he accorded to art. His object was not to lead art 

 captive to science ; but rather to unite them in an alliance of 

 mutual confidence and support. 



" The horizons of physics, philo;ophy, and art have," he said, 

 " been too widely separated, and, as a consequence, the lan- 

 guage, the methods, and the aims of any one of these studies 

 presents a certain amount of difficulty for the student of any 

 other of them." To smooth away these difficulties, to bridge 

 over the separating gulf, to supply the common language, were 

 the objects of the life-work of von Helmholtz. It was a noble 

 ideal, nobly pursued, and crowned with as much success as 

 could reward the efforts of one man. It is an ideal akin to that 

 which dominates this Institution, where science, literature, and 

 art are all heard in turns. 



If it is possible to sum up in a sentence the teaching of 

 von Helmholtz, and the work of his life, it is that, in spite of 

 the apparent diversities between science and science, between 

 science, philosophy, ani art, there is a fundamental unity, and 

 that the future is for thoie who detect, amid the seeming 

 discords of the schools, the true harmony which underlies and 

 dominates them all. 



ELECTRIFICATION OF AIR AND OTHER 

 GASES.^ 



§ I. AT the meeting of the British .Vssociation in Oxford in 

 ■'*■ August 1X94, a communication was given to Sec- 

 tion A, entitled "Preliminary Experiments to find if Subtrac- 

 tion of Waterfrom Air Electrifies it." These experiments were 

 performed during July of 1894, and were a continuation of 

 experiments which were commenced in the Physical Laboratory 

 of the University of Glasgow in December of 1S6S with the 

 same object, but which were then, for various reasons, dis- 

 continued before any decisive result had been obtained. 



1 A Paper liyLord K<^Ivin. P.R S., Magnus Maclean, and Alexander 

 Gall, read at the Royal Soc.cly on February 21. 



