yune6, 1878] 



NATURE 



163 



tial to the life of a University. "I appreciate," he say 5, "at 

 its full value this last advantage, when, looking back, I recall my 

 student days, and the impression made upon us by a man like 

 Johannes Miiller, the physiologist. When one finds himself in 

 contact with a man of the first order, the entire scale of one's 

 intellectual conceptions is modified for life ; contact with such 

 a man is perhaps the most interesting thing life may have to 

 offer." 



Now, the form in which Johannes Miiller stated what we may 

 regard as the germ which fertilized the physiology of the senses 

 is this, that the difference in the sensations due to different 

 senses does not depend upon the actions which excite them, 

 but upon the various nervous arrangements which receive them. 



To accept this statement out of a book, as a matter of dead 

 faith, may not be difficult to an easy-going student ; but when 

 caught like a contagion, as Helmholtz caught it, from the lips of 

 the living teacher, it has become the guiding principle of a life of 

 research. 



No man has done more than Helmholtz to open up paths of 

 communication between isolated departments of human know- 

 ledge ; and one of these, lying in a more attractive region than 

 that of elementary psychology, might be explored under excep- 

 tionally favourable conditions, by some of the fresh minds now 

 coming up to Cambridge. 



Helmholtz, by a series of daring strides, has effected a passage 

 for himself over that untrodden wild between acoustics and 

 music — that Serbonian bog where whole armies of scientific 

 musicians and musical men of science have sunk without filling 

 it up. 



We may not be able even yet' to plant our feet in his tracks 

 and follow him right across. That would require the seven 

 league boots of the German colossus ; but to help us in Cam- 

 bridge we have the Board of Musical Studies, vindicating for 

 music its ancient place in a liberal education. On the physical 

 side we have Lord Rayleigh laying the foundation deep and 

 strong in his " Theory of Sound." On the aesthetic side we 

 have the University Musical Society doing the practical work, 

 and in the space between, those conferences of Mr. Sedley 

 Taylor, where the wail of the siren draws musician and mathe- 

 matician together down into the depths of their sensational being, 

 and where the gorgeous hues of the phoneidoscope are seen to 

 seethe and twine and coil like the 



" Dragon boughs and elvish emblemlngs " 

 on the gates of that city where 



" an ye heard a music, like enow 

 They are building still, seeing the city is built 

 To music, therefore never built at all, 

 And therefore built for ever. " 



The special educational value of this combined study of music 

 and acoustics is that more than almost any other study it in- 

 volves a continual appeal to what we must observe for 

 ourselves. 



The facts are things which must be felt ; they cannot be learned 

 from any description of them. 



All this has been said more than two hundred years ago by one 

 of oiu: own prophets — William Harvey, of Gonville and Caius 

 College. ** For whosoever they be that read authors, and do 

 not by the aid of their own senses, abstract true representations 

 of the things themselves (comprehended in the author's expres- 

 sions) they do not resent tme ideas, but deceitful idols and phan- 

 tasms, by which they fi-ame to themselves certain shadows and 

 chimaeras, and all their theory and contemplation (which they 

 call science) represents nothing but waking men's dreams and 

 sick men's phrensies." 



Prof. Maxwell was assisted in his practical demonstrations by 

 Mr. Gamett, of St. John's College. 



SOCIETIES AND ACADEMIES 

 London 

 Physical Society, April 13.— Prof. R. B. Clifton, vice- 

 president, in the chair. — The following candidates were elected 

 Members of the Society :— W. Campbell, R. W. F. Harrison, 

 Rev. T. N. Hutchinson, M.A., B. W. Richardson, M.B., 

 F.R.S. — The Secretary read a paper by Messrs. J. Nixon and 

 A. W. Heaviside, describing their experiments on the mechani- 

 cal transmission of speech through wires or other substances, to 

 which Mr. Preece had referred at a previous meeting of the 

 Society. After describing a number of experiments in which 

 metallic discs soldered on to the ends of the conducting wires 



were employed, they went on to enumerate the more success- 

 ful experiments in which wooden discs were mainly employed. 

 The first actual transmission of speech was effected by placing 

 the belly of a violin against the receiving end of the wire, when 

 every syllable spoken was distinctly audible. Very good 

 results were obtained by employing mouth-and-ear pieces, 

 formed as in a telephone, the disc being replaced by thin wooden 

 discs, six inches in diameter, and a No. 4 wire was found to be 

 most satisfactory. On suspending a length of this wire in such 

 a manner that it had no rigid attachments, it was ascertained 

 that 120 yards is the limit through which a conversation can be 

 carried on. — Capt. Abney, F.R.S. , described the method he 

 adopted for photographing the least refrangible end of the 

 spectrum. He pointed out that it is impossible, with the ordi- 

 nary sensitive salts employed in the usual way, to photograph 

 further than the Fraunhofer line E, though by a preliminary 

 exposure to light of a Daguerrotype plate, Draper was 

 able to photograph beyond the extreme limit of visibility in 

 the red end of the spectrum. This method, however gave 

 what is known as a reversed picture, the lights and shades 

 being transposed, besides requiring a lengthened exposiure. 

 It enabled Becquerel to photograph the spectrum in its 

 natural colours, and later St. Victor obtained coloiured images 

 of colom-ed cloths. The object of Capt. Abney had been to 

 obtain unreversed pictures of this portion of the spectrum ; in 

 other words, to obtain a compound that would be similarly 

 sensitive to the red and the blue components of white light. 

 Such a compound he had at last obtained by what he termed 

 weighting silver bromide with resin, and now he obtains it by 

 causing the molecules of sUver bromide to weight themselves. 

 He showed an ordinary bromide of silver plate, and the colour 

 of the transmitted light was of a ruddy tint, showing absorp- 

 tion of the blue rays ; another film was shown containing 

 weighted bromide of silver, which transmitted blue light and 

 absorbed the red. Photographic plates prepared with the latter 

 compound he showed were sensitive to the red and ultra-red 

 waves of light, and he threw on the screen photographs of the 

 spectrum from the line C to a wave-length of 10,000, the ultra- 

 red showing remarkable groupings of lines. He fiu-ther showed 

 that by friction the blue film was changed to the red, and in that 

 state was not sensitive to the lower part of the spectrum. These 

 photographs were taken by means of a diffraction grating, and 

 Capt. Abney demonstrated Fraunhofer 's method of separating 

 the various orders of spectra produced by it. He then explained 

 that recently he had elucidated the reason of the reversal of 

 Draper's pictures by the least refrangi'ole end of the spectrum. 

 He finds that it is accelerated by exposing the plates in weak 

 oxidising solutions, such as those of hydroxyl, bichromate of 

 potash, permanganate of potash, and nitric acid, or exposure to 

 ozone. The red rays, in other words, seemed to oxidise the 

 photographic image, and to render it incapable of development. 

 — Mr. H. Bauermathen exhibited some paper models illustrative 

 of the disposition of the planes of symmetry in crystals. 

 These included octants of the sphere with inclosed cube 

 and octahedron faces pointed into their corresponding 

 hexakis-octohedral faces, a cubic skeleton built up from 

 nine planes of symmetry with a removable outer shell, and a 

 system of axial planes of an unsymmetrical mineral inclosing a 

 solid nucleus contained between three parallel pairs of planes. 

 They were constructed for the purpose of showing popularly the 

 difference between planes of symmetry and other diametral 

 planes by laying upon them a small mirror or plate of mica, 

 when in the first case the inclosed nucleus gave a symmetrical 

 image corresponding in position to the plane immediately behind 

 the mirror, but in the second a broken image is produced. — Dr. 

 Guthrie exhibited the arrangement of apparatus he had em- 

 ployed, in conjunction with his brother, to ascertain the effect of 

 heat on the transpiration of gases. The main difficulty connected 

 with the research was the securing of an absolutely constant 

 l^ressure on the air operated upon. This was secured by inserting 

 into the neck of the vessel which served as an air-chamber a tube 

 turned up at its inner end and terminating externally by a small 

 funnel ; as the tube was kept constantly full of water, the funnel 

 overfloAving, a pressure represented by the difference between the 

 heights of these levels was maintained. After passing through 

 a series of drying tubes the air traversed the (U-shaped) capillary 

 tube in a beaker containing water of known temperature, and 

 was finally received in an inverted tube contained in an overflow- 

 ing dish of water. Among other results it was found that the 

 resistance of a tube is the same as that of its several portions. 



