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NATURE 



I'/une 19, 1879 



rator at the expense of its tension by condensing the 

 charges." 



Passing on to details concerning the light itself, we are 

 told that the heating of the positive carbon to a higher 

 temperature than the negative (an effect which, by the 

 way, depends also upon the diameters of the two carbons) 

 by the battery current does not take place with currents 

 of high tension produced by induction machines. The 

 author makes Professors Ayrton and Perry responsible 

 for the statement that the resistance of the arc is 255 

 ohms. 



Again, on p. 25 we read that the Bu/ise/i's cell was dis- 

 covered in 1839 by Grove! And, on p. 34, that to ascer- 

 tain the resistance of the circuit a rheostat is employed. 

 We had hitherto imagined Prof. Bunsen's battery to be a 

 somewhat later device than that of Sir William Grove, 

 dating from 1842 or 1843, and that for all practical pur- 

 poses the unreliable rheostat had long been superseded 

 by reliable resistance-coils. We rub our eyes mentally 

 over these little matters. 



In one of the appendices some excellent remarks of 

 Mr. W. H. Preece are transcribed entire. In another a 

 brief account of Mr. Edison' s patent is copied from the 

 Standard, with the following comment : — " This patent, 

 practicable or not, exhibits the usual ingenuity of Mr. 

 Edison, says the Standards for our part we cannot share 

 this opinion, and can see nothing new in the patent. It 

 is a crude idea which does not seem to us likely to lead 

 to any important results." 



There is little doubt that to a large class of readers an 

 English translation of this work will be acceptable. It 

 will, however, require careful revision by a competent 

 editor, especially in those passages — numerous to an 

 almost irritating degree — where the reader is referred to 

 the previous works of the author. If this be done the 

 book will fill a useful place at the present time, when so 

 much ignorance prevails as to the nature of the electric 

 light 



Mr. Shoolbred's "Electric Lighting" is an expansion 

 of the papers read by him before the Society of Arts and 

 elsewhere, and professedly deals chiefly with the question 

 from the point of view of practical application. Hence 

 we have in this volume not only the well-known results of 

 experiments on the cost of the light in tabulated form, 

 but also paragraphs on such outlying subjects as photo- 

 meters, gas-engines, and water-motors. All the principal 

 machines and lamps are briefly described, and many of 

 them figured on lithographed plates. Under the heading 

 of Electric Candles, those of De Meritens, Wilde, and 

 Rapieff are mentioned in addition to the well-known 

 Jablochkoff " candles." Some account is also given of 

 the chief experiments recently made in this country on 

 the various systems of lighting. The manufacture of the 

 carbon pencils for producing the arc is very briefly 

 treated : too briefly, considering that this is the very 

 point in which there exists at present the greatest room 

 for improvement. 



Some of the expressions used by Mr. Shoolbred strike 

 us as warranted neither by their scientific accuracy, nor 

 by popular usage. Thus on p. 95 we find, on the question 

 of the subdivision of the light, the following sentence : 

 " The product of each electrical circuit may, it would 

 appear, be fairly considered as the unit of output." On 



p. 96 : " The output of a machine with regulators does 

 not readily divide itself." This term "output," which in 

 these instances, and on p. 11, is used for quantity of 

 current generated by the machine, occurs again on pp. 65 

 and 66 for the amount of light emitted ! The statement 

 on p. 50 that "the very production of the electric light 

 depends upon the conversion of a certain amount of 

 mechanical duty into electrical force," would certainly 

 draw down the wrath of sticklers for scientific accuracy. 

 The suggestion to produce the voltaic arc between incom- 

 bustible electrodes so as to avoid the production of 

 nilrous fumes, " and the very fact that the use of carbon 

 electrodes led to the development of s^tch baneful ejnana- 

 tions," can hardly be endorsed as a piece of chemical 

 wisdom. 



These blemishes, however, and a prevailing inelegance 

 of style, show that a general acquaintance with a scientific 

 subject will not alone qualify its possessor to be regarded 

 as an authority. 



For general merit and usefulness the treatise of Dr. 

 Higgs on the electric light in its practical applica- 

 tions will take high rank. Avoiding historical details 

 and points of abstract theoretical interest, the author 

 begins by describing the various lamps and "burners" 

 devised for producing electric light ; he then goes on to 

 enumerate the various generators, and to discuss their 

 relative efficiency and economy, illustrating every point 

 where possible by carefully tabulated results of experi- 

 ment ; and concludes with a notice of various useful 

 applications. Many sources of information have obviously 

 been laid under contribution ; the report of the Franklin 

 Institute, that of Professors Houston and Thomson, and 

 the very valuable paper of Mr. Preece on the question 

 of multiplication of lights, being reproduced almost entire. 

 The recent and instructive report of Dr. Oelhausen is 

 also quoted in the chapter on Commercial Aspects. 

 Chapter viii. is devoted to electric "regulators," a term 

 which we discover the author to apply to devices, not for 

 regulating the arc, but for controlling the strength of the 

 current. He rejects the term "regulator" in its usual 

 application, preferring to speak of electric "lamps" and 

 " burners.' ' On page 1 96 is given a table of the various and 

 singularly divergent measurements which have been made 

 of the intensity of illumination of the' Jablochkoff candle. 

 A summary of the report of the Gas Light and Coke 

 Company's Committee is also given, and the prejudiced 

 nature of that document is clearly demonstrated. A few 

 blunders require attention. Thus the formula on page 

 198 for estimating the useful effect of distributed lights is 

 hopelessly wrong. Again, while there is on page 169 a 

 statement that the light is proportional to the current, we 

 find on page 214 a sentence which would lead us to 

 imagine the author's opinion to be that the light was pro- 

 portional to the fourth power of the current ! We doubt, 

 too, whether it has yet been shown that " the hissing noise 

 produced by the electric arc is due to the formation of a 

 vacuum round the incandescent points." The statement 

 that "a tuning fork with its prongs two yards in length 

 will vibrate less than once in two seconds " is misleading, 

 and not necessarily true. These defects apart, the book 

 is a good one ; and the illustrations, which are numerous, 

 strike us as being, for the most part, superior to the 

 average of those of scientific books. But why should the 



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