94 



NATURE 



\yune 3, 1880 



or in schools for deaf-mutes who have many facts of 

 interest and value to contribute. It is only when these, 

 facts have all been gathered in that it will be possible to 

 reconstruct that primitive speech of mankind which pre- 

 ceded articulate utterance, which formed the bridge to 

 spoken language and expressed the earliest thought of 

 the human race. A. H. Savce 



TESTING TELEGRAPH LIhES 

 Instnu/ioiis for Testing Telegraph Lines and the Techni- 

 cal Arrangement of Offices. By Louis Schwendler. 

 Vol. ii. Second Edition. (London : Triibner and 

 Co., 1S80.) 



THE second volume of this useful work is free from 

 the defects which disfigured the first volume, and 

 which we were bound to find fault with (Nature, vol. xix. 

 p. 192). This is doubtless due to the watchful eye and 

 careful hand of Prof. M'Leod, who has nursed it through 

 the press and added some useful notes. It contains a 

 very full and clear description of Mr. Schwendler's modi- 

 fication of the tangent galvanometer, by which quanti- 

 tative electrical measurements of batteries, lines, and 

 apparatus are more rapidly though more roughly made 

 than with bridges and coils. Such an instrument is very 

 extensively employed in England and America, but Mr. 

 Schwendler has certainly improved its efficiency by 

 combining certain resistances with it and making it more 

 portable. It is remarkable what a handy and useful 

 instrument this becomes, and what a valuable help it is 

 to the telegraph engineer. Mr. Preece mentioned at the 

 Society of Telegraph Engineers the other evening that it 

 frequently happened over the extensive system of the 

 Post Office — 120,000 miles of wire and 12,000 instruments 

 — that the daily bill of health showed not one single fault 

 existing, and this he attributed principally to that accurate 

 system of testing which has been in use in England for 

 nearly twenty years. Mr. Varley introduced this system 

 in England and in America also, where it is very exten- 

 sively employed. It is a pity that Mr. Schwendler has 

 not made himself better acquainted with the systems in 

 use in other countries, for the perusal of his book leaves 

 the impression that he thinks he has inaugurated a new 

 system in India, whereas he has only modified existing 

 systems to suit the requirements of the Indian service. 

 Again this desire to be individual is shown by the adoption 

 of that most unnecessary nomenclature of unit current, 

 the " Oersted.-'' Unit current is now universally known 

 as the " Weber," and though some confusion has oc- 

 curred as to whether unit current should be " webers 

 per second," or simply "weber," nevertheless "webers" 

 and that useful sub-multiple "milliwebers " are now 

 used all over the world, except in India. Custom 

 only has forced the terms volt, ohvi, farad, weber into 

 use. He would be a bold man who would attempt to 

 convert " Ohm " into " Schwend," yet Mr. Schwendler 

 would convert "Weber" into " Oersted." There is no 

 doubt that Mr. Latimer Clark, who is the author of the 

 recognised nomenclature, proposed the term "weber" for 

 unit quantity, but as any term apphed to unit quantity, 

 excepting that based on unit capacity or "farad," is not 

 wanted, and unit current is unit quantity per unit time, 

 "webers per second" has rapidly, by the silent linguistic 



process of abbreviation, subsided into "webers," and 

 webers it will remain. This strange habit of ignoring 

 existing terms is shown in the definition of "intensity" 

 (p. 40) as applied to a battery which is said to be the 

 maximum current which a battery produces on short 

 circuit. Now there is scarcely an Erglish-speaking 

 country where this property is no' known as "quantity," 

 though this term is carefully excluded from all books from 

 its eminently unscientific character. Nevertheless it is so 

 rooted in telegraphic circles that there is scarcely a line- 

 man in all England that does not use it. Again, those 

 currents which every one knows as "earth currents" are 

 called in India " natural currents " (p. 53). Moreover we 

 have the strange anomaly that sometimes the author uses 

 Siemen's units, sometimes ohms, sometimes S.U., and 

 sometimes B.A.U., to designate units of resistance. 



The battery used in India is the Minotto form of 

 Daniell — a very wasteful cell, and giving for line purposes 

 an internal resistance of 30 ohms ! In dry climates where 

 the circuits are long such a battery may be useful, but in 

 damp climates, like England, where the circuits are com- 

 paratively short, such a battery is impossible. The 

 Minotto cell is, however, very constant in its electro- 

 motive force ; and Mr. Schwendler's instructions for its 

 maintenance are very clear and complete. 



The principal portion of the book is devoted to a 

 description and mode of construction and examination of 

 the instruments in use in India and their connections; 

 Mr. Schwendler has introduced a useful test called the 

 "range test," by which those currents are recorded 

 between which the instrument will work without any re- 

 adjustment. Thus the range test of a Siemen's relay is 

 25. In other words, whether the current used be "ooi or 

 •025 weber, or any current of intermediate strength, the 

 relay will equally work. An instrument that wall stand 

 such a test must be quite free from friction in its points or 

 from residual magnetism in its iron core. The working 

 currents in India never exceed 8 milliwebers nor fall 

 below 2 milliw'ebers. Hence if a relay fulfil the above 

 test it never wants adjustment. This is certainly "a con- 

 summation devoutly to be wished" by all telegraphists. 



We observe the following interesting instruction ; " On 

 no account are relays to be exposed to the direct rays of 

 an Indian sun. The permanent magnet is sure to lose its 

 magnetism perceptibly, and consequently the relay w-ill 

 become unsensitive." Is this due to the light or to the 

 heat of the sun 'i His notions of the efficiency of lightning 

 protectors are rather heterodox. " All," says he (p. 19S), 

 " that can be said of them at present is, that if they are 

 kept clean they do no harm ; ' ' yet he gives a very clear 

 description of those in use. He attributes to Steinheil, in 

 1S46, the first lightning discharger; but Highton, on the 

 London and North- Western Railway, before this, rapt the 

 wire for eight inches on each side of the instrument in 

 bibulous paper and surrounded it with a mass of metallic 

 fiUngs placed in a tin lined box in connection with the 

 earth. 



Very excellent descriptions are given of different forms 

 of relays and of various plans devised for reducing the 

 effects of induction, notably ?vlr. W. P. Johnston's electro- 

 magnetic shunt. Indeed the work is an admirable de- 

 scription of telegraphy in India, and it is one which 

 should be in every electrician's library. There are 



