September i, 1898] 



NATURE 



429 



denique instrumentorum auxilio, quae ipse aut primus invenerat 

 aut in melius mutaverat, multa accuratius investigavit, multa 

 prius ignota patefecit, in regiones novas scientiae suae terminos 

 feliciter propagavit. Ob imperii tanti fines tam late propagates 

 lauream nostram victori felici libenter decernimus. 

 Duco ad vos Hugonkm Kronecker. 



(8) In provincia Palatina physiologiae professor Heidelber- 

 gensis abhinc annos plus quam triginta corporis cellularum in 

 protoplasmate disputandi materiem satis amplam invenit ; 

 abhinc annos plus quam viginti de forma ' ' nervorum " in 

 musculos desinentium multum conscripsit ; abhinc annos 

 decem coram Societate Regia Londinensi de ea physiologiae 

 provincia disseruit, in qua vitae suae quasi tabernaculum 

 posuerat. Qui totiens unumquodque duorum lustrorum spatium 

 laboribus suis luculenter illustravit, quasi regulam vitae Hora- 

 tianum illud videtur sumpsisse : — 



" servetur ad imum 

 qualis ab incepto processerit, et sibi constet." 



Ergo etiam in posterum intra decem annos speramus physio- 

 logiae e provincia chemica fore ut talium virorum victoriis laurus 

 plurimae referantur. 



Duco ad vos WiLLELMUM KiJHNE. 



(9) Galliae ex Collegio Parisiensi laetamur adesse hodie his- 

 toriae naturalis professorem illustrem, qui, apparatu exquisite 

 adhibito, physiologiae quaestiones physicarum rationum ope 

 totiens explicavit. Idem non modo cordis palpitationem 

 alternam, sanguinis cursum continuum, musculorum denique 

 contractionem penitus exploravit, sed etiam animalium com- 

 plurium motus varios lucis ipsius auxilio feliciter illustravit. 

 Talium virorum dignitatem contemplata, Universitas nostra non 

 sine superbia quadam etiam in hunc virum quadrare confitebitur 

 verba ilia comoediae Gallicae celeberrimae in extremo posita : — 

 " dignus, dignus est intrare in nostro docto corpore." 



Novem virorum insignium seriem, non Senatus tantum nostri 

 praeconio dignatam, sed etiam collegarum suorum omnium 

 plausu comprobatam, claudit hodie professor illustris, 

 Stephanus Iulius Marey. 



Prof. Kowalevsky, the distinguished Professor of Zoology 

 in the Imperial University of St. Petersburg, was unfortunately 

 prevented from being present to receive the honorary degree of 

 Doctor in Science, which it had been proposed to confer on 

 him. In introducing the nine recipients of honorary degrees 

 who were present, the Public Orator adopted the reformed 

 pronunciation of Latin ; and his speeches were accordingly 

 readily understood and appreciated by the great concourse of 

 international visitors in the Senate House. 



EXPERIMENTS WITH THE TELEPHONE} 



T^ARLY estimates of the minimum current of suitable fre- 

 quency audible in the telephone having led to results 

 difficult of reconciliation with the theory of the instrument, 

 experiments were undertaken to clear up the question. The 

 currents were induced in a coil of known construction, either 

 by a revolving magnet of known magnetic moment, or by a 

 magnetised tuning-fork vibrating through a measured arc. The 

 connection with the telephone was completed through a resist- 

 ance which was gradually increased until the residual current 

 was but just easily audible. For a frequency of 512 the current 

 was found to be 7 x lo"* amperesXthe details are given in Phil. 

 Mag., vol. xxxviii. p. 285, 1894). This is a much less degree 

 of sensitiveness than was claimed by the earlier observers, but it 

 is more in harmony with what might be expected upon theoretical 

 grounds. 



In order to illustrate before an audience these and other 

 experiments requiring the use of a telephone, a combination of 

 that instrument with a sensitive flame was introduced. The gas, 

 at a pressure less than that of the ordinary supply, issues from a 

 pin-hole burner (the diameter of the pin-hole maybe 0'03") into 

 a cavity from which air is excluded (see Fig. l). Above the 

 cavity and immediately over the burner, is mounted a brass 

 tube, somewhat contracted at the top where ignition first occurs 

 (Camb. Proc, vol. iv. p. 17, 1880). In this arrangement the 

 flame is in strictness only an indicator, the really sensitive organ 

 being the jet of gas moving within the cavity and surrounded by 

 a similar atmosphere. When the pressure is not too high, and 

 the jet is protected from sound, the flame is rather Ull and burns 



1 A discourse delivered at the Royal Institution, on June 10, by the 

 Right Hon. Lord Rayleigh, F.R.S. 



bluish. Under the influence of sound of suitable pitch the jet 

 is dispersed. At first the flame falls, becoming for a moment 

 almost invisible ; afterwards it assumes a more smoky and 

 luminous appearance, easily distinguishable from the unexcited 

 flame. 



When the sounds to be observed come through the air, they 

 find access by a diaphragm of tissue paper with which the cavity 

 is faced. This serves to admit vibration while sufficiently ex- 

 cluding air. To get the best results the gas pressure must be 

 steady, and be carefully adjusted to the maximum (about i inch) 

 at which the flame remains undisturbed. A hiss from the mouth 

 then brings about the transformation, while a clap of the hands 

 or the sudden crackling of a piece of paper often causes ex- 

 tinction, especially soon after the flame has been lighted. 



When the vibrations to be indicated 

 are electrical, the telephone takes the 

 place of the disc of tissue-paper, and 

 it is advantageous to lead a short tube 

 from the aperture of the telephone into 

 closer proximity with the burner. The 

 earlier trials of the combination were 

 comparative failures, from a cause that 

 could not at first be traced. As ap- 

 plied, for instance, to a Hughes' in- 

 duction balance, the apparatus failed 

 to indicate with certainty the introduc- 

 tion of a shilling into one of the 

 cups, and the performance, such as 

 it was, seemed to deteriorate after a 

 few minutes' experimenting. At this 

 stage an observation was made which 

 ultimately afforded a clue to the 

 anomalous behaviour. It was found 

 that the telephone became dewed. 

 At first it seemed incredible that 

 this could come from the water of 

 combustion, seeing that the lowest 

 part of the flame was many inches 

 higher. But desiccation of the gas 

 on its way to the nozzle was no 

 remedy, and it was soon afterwards 

 observed that no dewing ensued if 

 the flame were all the while under 

 excitation, either from excess of pres- 

 sure or from the action of sound. 

 The dewing was thus connected 

 with the unexcited condition. Even- 

 tually it appeared that the flame in 

 this condition, though apparently filling up the aperture from 

 which it issues, was nevertheless surrounded by a descending 

 current of air carrying with it a part of the moisture of com- 

 bustion. The deposition of dew upon the nozzle was thus 

 presumably the source of the trouble, and a remedy was found 

 in keeping the nozzle warm by means of a stout copper wire 

 (not shown) conducting heat downwards from the hot tube above. 

 The existence of the downward current could be made evident 

 to private observation in various ways, perhaps most easily by 

 projecting little scraps of tinder into the flame, whereupon 

 bright sparks were seen to pass rapidly downwards. In this 

 form the experiment could not be shown to an audience, but the 

 matter was illustrated with the aid of a very delicate ether 

 manometer devised by Prof. Dewar. This was connected with 

 the upper part of the brass tube by means of a small lateral 

 perforation just below the root of the flame. The influence of 

 sound and consequent passage of the flame from the unexcited 

 to the excited condition was readily shown by the manometer, 

 the pressure indicated being less in the former state of things. 



The downward current is evidently closely associated with the 

 change of appearance presented by the flame. In the excited 

 state the gas issues at the large aperture above as from a reservoir 

 at very low pressure. The unexcited flame rises higher, and 

 must issue at a greater speed, carrying with it not only the 

 material supplied from the nozzle, and constituting the original 

 jet, but also some of the gaseous atmosphere in the cavity sur- 

 rounding it. The downward draught thus appears necessary in 

 order to equalise the total issue from the upper aperture in the 

 two cases. 



Although the flame falls behind the ear in delicacy, the com- 

 bination is sufficiently sensitive to allow of the exhibition of a 

 great variety of interesting experiments. In the lecture the 

 introduction of a threepenny-piece into one of the cups of a 



NO. 1505, VOL. 58] 



