98 



NA TURE 



IDec. 3, T885 



so frequently been referred to by former writers as being 

 present in cholera dejecta : the comma being, in short, 

 nothing more than a segment of one of these vibrios which 

 had become detached during the process used by Koch. 

 It is true that Koch's friends deny that any comma found 

 elsewhere than in the cholera intestine grows under culti- 

 vation, in the same way as the one he has described, but 

 so far, this is a mere assertion, not a proved fact ; and it 

 is evident that we are Ijut at the commencement of any 

 proper apprehension as to the significance of these vibrios. 

 This is pointed out in an appendix to the Committee's 

 report, and the lines of future investigation into the sub- 

 ject are laid down. But for the present the prevention 

 of cholera can only be found in the prosecution of well- 

 advised sanitary measures, and whilst it is of the utmost 

 importance that labours such as Koch and former inves- 

 tigators have carried out should be continued and put to 

 the most rigid test, yet micro-pathology cannot, at 

 present, be regarded as having made more than a small 

 advance towards the solution of the question under 

 discussion. 



A MANUAL OF TELEGRAPHY 

 A Manual of Tclegraplty . By W. Williams, Superin- 

 tendent of Indian Government Telegraphs, &c. (Lon- 

 don : Longmans, 18S5.) 



ANfANLTAL compiled to order for the use of the 

 employes of the Department — very well written, 

 very well printed, very useful to the Department, and 

 very interesting to the technical reader. It embraces a 

 general description of the apparatus used in India, the 

 faults they experience, and the remedies they apply ; a 

 full account of the elaborate system of testing reared 

 under the care of the late Louis Schwendler, the able 

 electrician of the Department ; and a clear account of 

 the electrical phenomena which interfere with telegraph 

 working and require watching and removal. 



It is supplemented by an excellent resume of the laws 

 which determine the strength of electric currents under 

 various circumstances, and a series of formute and 

 mathematical solutions of various problems that occur in 

 practice. It is in reality a primer to an admirable work 

 on '■ Testing," written by Schwendler and edited by 

 another very able electrician who died in India — R. S. 

 Brough. 



It is remarkable how India, practically isolated tele- 

 graphically from the rest of the world, originated and 

 nraintains a system sui gc7ieris. It was sown by 

 O'Shaughnessy, it was nursed by Robinson, it is main- 

 tained by Cappel. It has had engrafted upon it much of 

 the German element, due to the education of Schwendler 

 in the great house of Siemens ; but it remains quite dis- 

 tinct from the rapid system in use in England, and also 

 from that in America— more Continental than English, and 

 Am.erican only in its long circuits and sound reading. 

 It has been singularly fortunate in the able officers that 

 have served it, most of whom are highly educated gentle- 

 men selected by competitive examination, and well 

 trained in technical matters before assuming office. The 

 proceedings of our societies, especially those of the 

 Telegraph Engineers, contain frequent valuable com- 

 munications from India, and this last volume fully 

 maintains the reputation of the Department. 



There are some curious errors, particularly among 

 those rocks upon which so many young writers are 

 wrecked, viz. definitions. 



There is a strange, but excusable, confusion between 

 electrification o.nA potential, while there is an inexcusable 

 confusion between curretzt and quantity. Definition I 

 says " electric guatitity'K the amount of electricity present 

 in an electrified body," and definition 2 says "the unit of 

 quantity or current is called an " Ampere, Weber, or 

 Oerstedt." Now the unit of quantity is called a coulomb, 

 and current is not quantity, but quantity per second, a 

 very diffisrent thing, and is called an ampere only. It 

 was called a weber, but this term has quite died out 

 since the Paris Congress of 1881, and no one ever called 

 it an oerstedt out of India. The relation between quantity 

 and current is shown by Faraday's great law : — 



Q= Ct 



It is a pity that p. 5 cannot be reprinted. Definition 16 

 is curiously worded : " The unit by which capacity is 

 measured is called a farad, or more generally for con- 

 venience a microfarad." A casual reader would think 

 that the same unit is indifferently called a farad or a 

 microfarad, whereas we learn later on that the one is one- 

 millionth of the other. 



.\t p. 57 we read of a very strange practice. The only 

 cause of errors in the signalling of figures (on which, it 

 must be remembered, the most important issues may 

 depend) is due to a practice, unfortunately too common, 

 known as "exaggerating signals," by which a letter is 

 given more characters than it really possesses : for 

 example, the letter h, a most common victim of this ill- 

 treatment, is, by the addition of an extra dot, mutilated 

 into the figure 5. We trust this strange practice is 

 confined to India ; we have never heard of it anywhere 

 else. 



The resume of laws at p. 241 is very good indeed:; but 

 why denominate Ohm's and Kirchofif's laws, and not 

 those of Ampere and Faraday ? 



The novel practice, in technical books, of printing 

 notes as well as references on the margin instead of at 

 the bottom of the page, has been adopted, and the con- 

 venience is certainly very considerable. The printing and 

 get-up of the book are admirable. It should be added to 

 every telegraph engineer's library. 



OUR BOOK SHELF 



Elements of Inorganic Chemistry. By James H. Shepard, 

 Ypsilanti High School. (Boston : D. C. Heath and 

 Co., 1885.) 



This little book is evidently intended as a sort of mutual 

 companion of the teacher and student, and is for be- 

 ginners only, as the author informs us. It is, however, a 

 mixture of elementary and somewhat advanced infonna- 

 tion on the subject, and certainly would be somewhat 

 difficult for a beginner to be left alone with. The book is 

 well supplied with questions for the student to attempt, 

 and also with suggestions to the teacher as to where 

 questions may be with advantage put. Most of the sub- 

 stances known as elements are mentioned, and their 

 properties to some extent described, even including the 

 so-called rare metals. A chart of " The Natural Classi- 

 fication of the Elements," according to " Mendelejeff," 

 and an appendix on reagents is also included. 



