544 



NATURE 



[June 30, 1910 



resistance of the conductor be not too great, it may 

 degenerate into a low-toned imitation of speech, or with 

 the smaller conductors which are used for city work the 

 attenuation rapidly lowers the volume of sound until it 

 becomes unrecognisable. Self-induction is the analogue of 

 inertia in mechanics ; therefore, if it were possible to 

 endow the circuit in which a wave was in movement with 

 sufficient self-induction to prevent the tailing and con- 

 sequent distortion of its form, the limit of speech would 

 be materially increased, as the attenuation due to resist- 

 ance alone would have to be provided for. Now it is 

 possible to achieve this result to a certain extent by adding 

 artificially to the self-induction of telephone cables, 

 technically termed loading. The ideal method would be to 

 increase the self-induction uniformly throughout, and 

 attempts have been made to effect this by lapping a copper 

 conductor with thin iron wire or tape of a high magnetic 

 permeability. Another method consists in distributing 

 magnetic coils at uniform distances of a mile or two apart 

 throughout the length of the line. Under these conditions 

 the distance over which speech is possible has been increased 

 from two and a half to three and a half times. 



The British Post Office has recently laid a cable with 

 distributed inductance between England and France which 

 will increase the range of speech about four times as com- 

 pared with a similar type of unloaded cable. 



The rapid and enormous development of the telephone 

 service that has taken place throughout the world within 

 the last few j-ears is a remarkable achievement of the 

 electrical engineer. The principle of the microphone, which 

 converts sound vibrations into electrical vibrations, and of 

 the telephone, which re-converts the electrical into sound 

 vibrations, are so well known that I need not dwell further 

 on the subject than to point out that Graham Bell's tele- 

 phone, as it left his hands in 1876, is essentially the same 

 instrument, slightly improved in mechanical construction, 

 as he gave it to the world, but all the other adjuncts of a 

 complete telephone service have been profoundly modified, 

 and we are not yet in sight of finality. 



In the period during which the ordinary telephone equip- 

 ment has undergone modifications, inventors have turned 

 their attention to the design and perfection of an auto- 

 matic telephone in which each subscriber, by a simple 

 method of manipulation, may without the intervention of 

 an operator at the exchange obtain direct access to any 

 other subscriber connected with the service. One of the 

 earliest systems of this type was known as the Strowger. 

 Each subscriber's line terminates on a line switch which 

 forms part of a group of 100 switches. This switch is 

 connected by ten circuits, the equivalent of the plugs and 

 cords in a manual board, with a series of selectors each 

 accommodating 100 junction lines. According to the size 

 of the exchange, there may be two or three sets of selectors 

 connected similarly by means of junction circuits, and, 

 finally, there is a connector, a somewhat similar instru- 

 ment, which makes the connection between the two 

 subscribers. 



Each telephone has a dial with finger holes and numbers. 

 On removing the telephone from the hook the procedure 

 is as follows. If, say, No. 4852 is wanted, the caller 

 inserts his finger in hole 4 and revolves the dial up to the 

 limiting stop. This actuates the line switch, which causes 

 a connecting plug to enter the springs of the first dis- 

 engaged junction leading to the selector group of 4000. 

 The same action follows in sequence with 8, 5, and 2, the 

 final movement of the connector making the connection if 

 the required subscriber is disengaged. If he be through 

 to another a busy back signal (a vibratory current) is 

 given. When the connection is made and the conversation 

 is complete, the hanging up of the telephones restores the 

 connections to the normal. This method has had consider- 

 able development amongst the independent telephone com- 

 panies in America. 



On the subject of the future development of telegraphs 

 and telephones, few of those acquainted with the subject 

 would venture to dogmatise, but certain statistics I have 

 prepared will convey to you possibilities far more pregnant 

 than any amount of speculation. The following figures, for 

 the years 1902 and 1907 respectively, have been gathered 

 from authentic returns, and they embrace information from 

 every country of importance throughout the world : — 



Telegraph and Telephone Statistics — Wire Mileage. 



Telegraphs 1902 1907 Increase 



Land wires 3>659>659 ... 5,038,981 ... 1,379,322 



Submarine cables 213,894 ••• 259,000 ... 46,io6 = 2rC ' 



'1 clephoncs 



Wire 7,467,417 ... 19,83^,537 ... 12,372,120 



Subscribers' stations ... 3,534,036 ... 8,406,336 -.. 4>873i33° 



Large figures frequently fail to impress the mind, but when 

 it is stated that this mileage of wire will soon, if it has 

 not by this time, equal one-third the distance from the 

 earth to the sun, the remarkable activity of the modern 

 telegraph and telephone service will perhaps be more 

 forcibly realised. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 

 Birmingham. — ^The engineering department is losing th^ 

 services of Mr. F. H. Hummel,, lecturer in civil engineer- 

 ing, who has accepted the chair of engineering at Belfast, 

 and of Dr. J. D. Coales, lecturer in electrical engineering, 

 who has been appointed principal of the Wolverhampton 

 Technical School. 



Cambridge. — The observatory syndicate, in a report to 

 the Senate on the Huggins dome and the astrophysical 

 building, state that the buildings now erected may be re- 

 garded as consisting of two parts, though for the sake of 

 economy in construction they are structurally blended. 

 The first part consists of a dome 23J feet in diameter, 

 together with a small room for accessory apparatus and 

 a room for any observer who may be making use of the 

 Huggins instruments installed in the dome. These are to 

 be called the Huggins dome and the Huggins observer's 

 room. The second part — the astrophysical building— com- 

 prises a computing room, which also serves as a library, 

 and a small room appropriated to the use of the head of 

 the department. The Huggins instruments are now ready 

 for adjustment and use. 



The Goldsmiths' Company have given 700!. for the equip- 

 ment of the metallurgical department of the chemical 

 laboratory. 



The prize of 50^. out of the Gordon Wigan fund fof 

 a research in chemistry has been awarded to Mr. J. 

 Thomas, Trinity, for experimental investigations on " The 

 Isolation of the Aromatic Sulphinic Acids" and "The 

 Resolution of Externally Compensated Quinoline^ Deri- 

 vatives containing Two Asymmetric Carbon Atoms." 



Mr. W. F. Pen^e, of the Indian Forestry Service, will 

 deliver a course of lectures on Indian forestry during the 

 Michaelmas term of 19 10. 



Oxford.— The next award for the Radcliffe prize will 

 be made in March, 1911. The prize, which is of the 

 value of 50I., is awarded by the master and fellows of 

 University College every second year for research in any 

 branch of medical science comprised under the following 

 heads :— human anatomy, physiology, pharmacology, 

 pathology, medicine, surgery, obstetrics, gynaecology, 

 forensic ' medicine, hygiene. The prize is open to ah 

 graduates of the University who shall have proceeded or 

 shall be proceeding to a medical degree in the University. 

 Candidates must not have exceeded twelve years from the 

 date of passing the last examination for the degree of 

 B.A., and must not, at the date of application, be fellows 

 on the foundation of Dr. John Radcliffe. The memoirs 

 must be sent to the University Registry on or before 



December i. , r ,' ■. • ^ 1 



The Rolleston memorial prize, the value of which is boi., 

 will be awarded in Easter or Trinity term, 1912. The 

 prize is open to such members of the Universities of Oxford 

 and Cambridge as will not have exceeded ten years from 

 the date of their matriculation on March 31, 1912, and is 

 to be awarded for original research in any subject com- 

 prised under the following heads :— animal and vegetable 

 morphology, physiology and pathology, and anthropology, 

 to be selected bv the candidates themselves. Candidates 

 wishing to compete should forward their memoirs to the 

 registrar of the University before March 31, 1912. The 

 memoirs should be inscribed " Rolleston Memorial Essay, 

 and should each bear the name and address of the author. 

 They mav be printed or in manuscript, memoirs already 

 pubfishedbeing aJmitted to the competition. 



NO. 2122, VOL. 83] 



