Oct. 17, 1878] 



NATURE 



651 



indefinitely, for the distribution of light and power appears to 

 have taken the public by surprise, and has exercised a most de- 

 pressing influence upon the holders of gas shares. Having given 

 close attention to the question of electric lighting ever since 

 1867 — when, following the researches of my brother, Dr. 

 Werner Siemens, I presented a paper to the Royal Society de- 

 scribing the dynamo-electric principle — I may be allowed per- 

 haps to make a few remarks upon the novelty and probable 

 effect of Mr. Edison's startling announcement. 



In passing an electric circuit from a main conductor into 

 several or any niunber of branches, the current divides itself 

 between those branches, according to the well-known law of 

 Ohm, in the exact inverse ratio of the electrical resistance pre- 

 sented by each branch. A current may thus be divided, for 

 instance, into ten separate currents cf precisely equal force, if 

 each branch is made to consist of a wire of the same length and 

 conductivity ; but if one of these wires was again to be slit into 

 ten wires, presenting in the aggi-egate the same conductivity, 

 each of these wires would only convey looth part of the total 

 current. In the same way one of the minor wires might again 

 be subdivided into branches, each of which would convey an 

 amount of electric current which would be accurately expressed 

 by the relative resistance of the branch in question, divided by 

 the total resistance of all the branches put together. It would 

 thus seem that nothing could be more easy than to divide a 

 powerful electric current among as many branches of vary- 

 ing relative importance as might be desired ; but in the case 

 of electric lighting a difficulty arises in consequence of the 

 varying resistance of each electric light or candle, due to the 

 necessarily somewhat varying distance of the carbon points from 

 each other, upon which the length of the luminous arc depends. 

 In order to work a number of lights upon different branches of 

 the same ciurent, it is necessary to furnish each branch with a 

 regulator so contrived that an increase of current corresponding 

 to too near an approach of the carbon points will produce auto- 

 matically an increased resistance in that branch circuit, whereas 

 an accidental increase in the distance between the carbon points 

 of any lamp will cause the regulator to reduce the extraneous 

 resistance of the cuxuit to z. viinivium. Such a mode of regu- 

 lating currents was present in my mind when, in addressing the 

 Iron and Steel Institute in March, 1877, I ventm-ed to express 

 my conviction that natural forces, such as represented by large 

 waterfalls, could be utilised for the production of motive power 

 and electric light, in towns at a distance even of thirty miles 

 from such source, by means of a large electric conductor. This 

 suggestion gave rise to a good deal of discussion and criticism, 

 especially in the United States ; but I replied to some of these 

 criticisms in delivering one of the Science Lectures at Glasgow 

 in March last, having already referred to the matter in a dis- 

 cussion that was held before the Institution of Civil Engineers 

 on January 29 last. Having in the meantime perfected the 

 regulator, I showed it in operation at the soiree of the Royal 

 Society on June 19, and have only been waiting to get 

 experimental data complete in order to bring the whole 

 subject before one of the scientific bodies. The arrange- 

 ment may be said to consist simply of a thin strip of 

 copper or silver, say six inches long and half an inch broad, 

 stretched horizontally between two supports with a weight or 

 spring exerting a certain pressm-e in the middle. The branch 

 current to be regulated is passed through this strip of metal, 

 which is thereby heated to a certain moderate extent, depending 

 upon the amount of current passing, and upon the rate of radia- 

 tion of the heat produced in the strip to surrounding objects. 

 Suppose that when the normal condition of things obtains, the 

 strip of metal is maintained at the temperature of, say, 100' 

 Fahrenheit, and suppose that by an accidental approach of the 

 carbons of a lamp the resistance of the circuit is suddenly de- 

 creased, an almost instantaneous increase of temperature of the 

 thin strip will ensue, which will cause it to elongate slightly, 

 and allow the weight resting in the middle to descend, which in 

 its turn causes an increase in the resistance of a small rheostat, 

 through which the branch current in question has to flow. 



It will thus be seen that it is not so much the novelty of the 

 announcement made by Mr. Edison as the manner in which it 

 has been conveyed to us that has alarmed a portion of the 

 British public, and I hold that such startling announcements 

 as these should be deprecated, as being unworthy of science 

 and mischievous to its true progress. 



Although I am strongly of opinion that electricity will gradually 

 replace gas in many of its most important applications as being 



both cheaper and more brilliant, I still hold the opinion, quoted 

 by Mr. Northover in his letter to you of yesterday, that its appli- 

 cation will be limited, at least during our generation, to such larger 

 purposes as the lighting of our coasts, to naval and military sig- 

 nalling, to harbours, quays, warehouses, and public buildings, in- 

 cluding perhaps picture galleries and drawing-rooms, where the 

 objections to gas are already felt to the extent of banishing that 

 means of lighting to the passages, offices, and bed-rooms. I 

 am, however, of opinion that a revolution even to the extent 

 indicated must be the work of time, and that while gas will un- 

 doubtedly in due course be supplanted by its more brilliant 

 rival for the purposes just indicated, the consumption of gas 

 will be maintained by the increasing area of application result- 

 ing from increase of towns, and by additional applications for 

 cooking and for heating purposes, for which gas will supplant 

 the use of solid fuel, and thus confer a new benefit upon man- 

 kind by doing away with the nuisance of smoke and ashes. If 

 gas companies only rightly understood their interests they would 

 themselves take up electric lighting for those purposes for which 

 it has the decided preference, and at the same time promote the 

 application of gas for heating, in doing which they would clearly 

 increase theu* business as lighting companies, while benefiting 

 the public by providing them with the very best sources of heat 

 and light. 



NOTES 

 At the request of the Chemical Society Prof. Ad. Wurtz, of 

 Paris, has accepted the office of Faraday lecturer for this year. 

 The subject of his lecture is "La Constitution de la Matiere a 

 I'Etat gazeux." The lectm-e is to be delivered on Tuesday, 

 November 12, in the Theatre of the Royal Institution, Albe- 

 marle Street. On the following day the Fellows of the 

 Chemical Society propose entertaining Prof. Wurtz at a dinner 

 to be held at Willis's Rooms. 



Those interested in the progress .of natural science at our 

 old universities should take notice of the fact that, after con- 

 siderable opposition of the "Board of Studies of the Natural 

 Science School," the majority of that Board (chiefly by the aid 

 of the examiners, who are London, and not Oxford, men) have 

 carried a series of resolutions which provide that "candidates 

 for honours in biology " may be examined in experimental 

 physiology. • The necessary encouragement to the study of this 

 subject, viz., examination in it as an "honour subject" now 

 existing, we may hope to see as the result some activity in 

 the physiological laboratory of Magdalen College. Similarly we 

 have to notice the recognition of the morphology and physiology 

 of the vegetable kingdom as a necessary part of the study 

 and examination of the Oxford student who is a candidate 

 for "honours in biology." Botany was long resisted and sneered 

 at in Oxford. External pressure has, however, reinstated botany 

 in the Oxford school of natural science, and it rests \\ ith the 

 examiners in future to maintain the study of this subject in the 

 direction indicated by Sachs' admirable treatise on Botany pub- 

 lished by the University press. 



The foUowng changes are proposed to be made in the 

 Council of the London Mathematical Society for the ensuing 

 session :— Mr. C. W. Merrifield, F.R.S., to be president in the 

 room of Lord Rayleigh, F.R.S., v.ho is proposed for the office 

 of vice-president in conjunction with Prof. Cayley, F.R.S. ; 

 Messrs. J. Hopkinson, F.R.S., and H. M. Taylor to be ordi- 

 nary members of council in the room of Prof. Clerk Maxwell, 

 F.R.S., and Mr. T. Cotterell. The valedictory presidential 

 address will probably be delivered at the annual meeting 

 (November 14). 



The new specimen of Archaopieryx lithographiciis of Solen- 

 hofen, the discovery of which was announced some tioie back, 

 has been purchased by Dr. Otto Folger, President of the Freie 

 Deutsche Hochstift, for the sum of 35,000 marks (1,750/.), and 



