Sept. 1, 1882.] 



• KNOWLEDGE 



227 



the innumerable solar systems of -which the universe is 

 composed." We are not told what would be the extreme 

 tenuity of such matter necessary that even the nearest 

 sun should show his light through twenty millions of mil- 

 lions of miles of it, or of what possible benefit the action 

 of rays on matter midway between our own sun and the 

 nearest sun (i.e. matter ten billions of miles from either) 

 could possibly be to the systems circulating either around 

 our own sun or around Alpha Centauri (and the like for 

 other stellar neighbours not quite so near). Still, — No 

 matter. In a vague sort of way, we may be able — at 

 least Dr. Siemens says we may — "to trace certain con- 

 ditions of thermal dependance and maintenance, in which 

 •we may recognise principles of high perfection, applicable 

 also to comparatively humble purposes of human life. So 

 then" (though the sequitur ma.y not be very obvious to all, 

 the idea itself is worthy of all praise), " we fellow-workers 

 in every branch of science my exhort one another in the 

 words of the American bard who has so lately departed 

 from among us : — 



Let ns then be np and doing, 

 With a heart for any fate ; 



Still achieving, still pursuing. 

 Learn to labour and to wait. 



Mathematical Section. 

 From the address by Lord Rayleigh, president of this 

 section, we extract the following well-considered reaiarks : 

 — " In one important part of the field of experimental 

 science, where the subject-matter is ill understood, and the 

 •wrork is qualitative rather than quantitative, success 

 depends more directly upon sagacity and genius. It must 

 be admitted that much labour spent in this kind of work 

 is ill directed. Bulky records of crude and uninterpreted 

 observations are not science, nor even in many cases the 

 raw material out of which science will be constructed. The 

 ■door of experiment stands always open ; and when the 

 question is ripe, and the man is found, he will, nine times 

 out of ten, find it necessary to go through the work again. 

 Observations made by the way, and under unfavour- 

 able conditions, may often give rise to valuable sug- 

 gestions, but these must be tested by experiment in 

 ■which the conditions are simplified to the utmost, 

 before they can lay claim to acceptance. When an 

 unexpected effect is observed, the question will arise 

 whether or not an explanation can be found upon admitted 

 principles. Sometimes the answer can be quickly given, 

 but more often it will happen that an assertion of what 

 ought to have been expected can only be made as the result 

 of an elaborate discussion of the circumstances of the case, 

 and this discussion must generally be mathematical in its 

 spirit, if not in its form. Tliis is shown by the investiga- 

 tions of the well-known experiment of the inaudibility of a 

 bell rung in vacuo. Leslie made the interesting observation 

 that the presence of hydrogen was inimical to the produc- 

 tion of sound. Years afterwards Stokes proved that what 

 Leslie observed was exactly what ought to have been 

 expected. The addition of hydrogen to attenuated air 

 increases the wave-length of vibrations of given pitch. 

 Examples such as this, which might be multiplied ad 

 libitum, show how dithcult it often is for an experimenter 

 rightly to interpret his results without the aid of mathe- 

 matics. The experimenter himself should be in a 

 position to make the calculations to which his work 

 gires occasion. I should like to see a course of mathe- 

 naatical instruction arranged with especial reference to 

 physics, within which those whose bent was plainly 

 towards experiment might, more or less completely, confine 

 themseJiTS. Probably a year spent judiciously on such a 



course would do more to qualify the student for actual 

 work than two or three years of the usual mathematical 

 curriculum. On the other side, it must be remembered 

 that the human mind is limited, and that few can carry the 

 weight of a complete mathematical armament without some 

 repression of their energies in other directions. The dif- 

 ferent habits of mind of the two schools of physicists 

 sometimes lead them to the adoption of antagoni.stic views 

 on doubtful and diflicult question.s. The tendency of the 

 purely experimental school is to rely almost exclusively 

 upon direct evidence. The tendency of the mathematician 

 is to overrate the solidity of his theoretical structures, and 

 to forget the narrowness of the experimental foundation 

 upon which many of them rest." 



Chemical Section. 

 In the course of his address to this section by Professor 

 Liveing, the following interesting remarks were made on 

 two matters which have recently been the subject of con- 

 troversy, now regarded, however, as disposed of. " When 

 we find that the combinations of particles of the same 

 kind are as definite as those of particles of different kinds, 

 and that they are both subject to precisely the same me- 

 chanical laws, we are hardly justified in regarding the 

 forces by which they are produced as essentially different 

 To get rid of a gratuitous hypothesis in chemistry must be 

 a great gain. But, it may be asked, why stop here 1 Why 

 may not the chemical elements be further broken up by 

 still higher temperatures'? .-1 priori, and from analogy, 

 such a supposition is extremely probable. The notion 

 that there is but one elementary kind of matter is at least 

 as old as Thales, and underlies Prout's hypothesis that the 

 atomic weights of our elements are all multiples of that of 

 hydrogen. This famous hypothesis has gone up and down 

 in the scale of credibility many times during the present 

 century. Quite recently," said the speaker, " a fresh re- 

 vision of the combining weights has been made on the 

 other side of the Atlantic by Professor F. W. Clarke, who, 

 on the whole, concluded that Prout's hypothesis, as modified 

 by Dumas, is still an open question — that is to say, his . 

 final numbers differ from whole multiples of a common 

 unit by quantities which lie within the limits of errors of 

 observation and experiment. Let us turn again to the 

 evidence afforded by our most powerful instrument for in- 

 specting the inner constitution of matter, the spectroscope. 

 A few years ago ^Ir. Lockyer supposed that the coincidence 

 of rays emitted by different chemical elements, particularly 

 when those rays were developed in the spark of a powerful 

 induction coil and in the high temperatures of the sun and 

 stars, gave evidence of a common element in the compo- 

 sition of the metals, which produced the coincident ra.ys. 

 Later results cannot fail to shake our belief in the exist- 

 ence of any common constituent of the chemical 

 elements ; but it does not touch the evidence which the 

 spectroscope affords us that many of our elements, in 

 the state in which we know them, must have a very com- 

 plex molecular structure. The spectroscope has in the 

 last few years revealed to us several new metals. AVhy 

 may there not be elements which, while they diller as littl* 

 in atomic weight as do nickel and cobalt, are, on the 

 other hand, so similar to one another in all characters that 

 their chemical separation is a matti^r of the greatest ditfi- 

 culty, and their difference only distinguishable by the spec- 

 troscope 1 The spectra may bo thought to suggest so much, 

 and how shall we decide the question 1 At any rate, the 

 complications of the spectroscopic problem can only 

 be unravelled by the united efforts of chemists and 

 physicists, and by the exercise of extreme caution." Prof. 

 Liveing said he could not dismiss the subject of chemical 



