22 JULY 1882, Page 21


'Tuts little book is one of a class that is very acceptable just now. It is a translation of a semi-popular work by the great French electrician, Du Moncel, and may be considered as a com- panion volume to the author's authorised translation. of The Telephone, the Microphone, and the Phonoga•caph. But it is very certain that if the works of Du Moncel are worth translating at all—a fact which cannot be questioned—they are worth receiv- ing more careful attention than Mr. Routledge has bestowed on the volume before us. We do not mean to say that the original has been misrepresented, but that the translator has not taken the trouble to correct his work. Mr. R.outledge would do well to remember that the care bestowed on a translation should be pro- portional to the value of the original, rather than to the price of the translated publication. The Expose des Applications de l'Electi•icite, by the same author, are referred to sometimes as `my' "Expos6," and at others as 'our' "Expos:5," and these alter- nations are so frequent, as to catch the eye and cause annoyance. Again, on two succeeding pages, we read " under a motive * Electric Lighting. Translated from the French of Le Comte H. du Mouoel by Robert Routlodge, B.So, Lend, With 711 Illustrations. London Georgo ledge and Bose.

power of 2i horse-power," and "parts is arranged ;" and again, in making an extract from a report presented to the London Metropolitan Board of Works, we read,—" According to the same report, the luminous power of these candles in Carcel lamps is : for the naked light, 39'8, horse-power." Of course, cancels are meant, but these mistakes have no excuse ; and we hope, in a new edition, these and similar points may be at- tended to. It is astonishing that more attention has not been paid to the translation of standard electrical works, the desirability for which there is internal evidence in the volume before us. Thus, in describing the Sawyer-Man lamp, the author says,—" We think it unnecessary to say more about it, than to express our surprise that English and Ameri- can inventors trouble themselves so little about the earlier inventions." In some cases, no doubt, the inventors may have been careless, though often simply through ignorance, in some cases even dishonest; but in many cases the more recent inventors have been well informed as to what had been done before them, and considered their own inventions to be improvements thereon,—a point on which Du Moncel may not always agree with them. Lately, it is true, our electrical con- temporaries have given translations of papers contributed to Continental scientific institutions and publications, and electrical book-makers with a knowledge of French have made a remark- ably energetic use of their knowledge on more than one occasion ; this is amusingly exemplified by the saying of an English electrician of some note, whilst recently recommend- ing the study of an American work to a pupil :—" It is chiefly cribbed from the French of Du Moncel, but it is none the worse for that." The translator recommends his readers who may be altogether new to his subject to acquire a few elementary facts prior to the perusal of this work ; and here we quite agree with him. Electricity, like any other practical scientific subject, is difficult to handle neatly ; and we think, perhaps, that the present volume has too wide an aim, much of the subject-matter it contains being of so purely scientific a nature as to be uninteresting to ordinary readers, whilst electricians will regret. that it does not contain more of the same character ; we should be glad, therefore, to see the present volume followed by a translation of a larger work by the same author, which we alluded to above, Expos6 des _Applications de l'Eleciricite, to which repeated reference is made in the present work. In the translation, we think it would have been well to discard the French method of expressing resistance by its equivalent in metres of telegraph wire, and to have adhered to the now familiar " ohm." And we further think the work would have been of greater value to English readers if the French measures, which are used through- out, had been exchanged for their English equivalents ; for although, as the translator states in his preface, French mea- sures are now universally adopted for scientific purposes, still in all matters of engineering and finance it is otherwise, and the present work is more practical than scientific.

The work is divided into six parts, the first of which is chiefly explanatory. In it we find a distinction drawn between "tension" and "potential," which, as it is often ignored, we give in full :—" The tension, of a current, which is now often confounded with the potential, is the property of the elec- tric fluid, which, in a manner, gives the impulse to the electrical movement, and which outwardly manifests itself by a tendency to act on the adjoining objects, and to produce the effects peculiar to static electricity. It is the quantity of electricity kept free at the poles of a battery when these are not connected, and which escapes recomposition during the time that the dis- engagement of electricity continues. The potential of a source of electricity is related to the tension ; but, being applied to the electrical actions themselves, it may represent the tension under more defined conditions, which admit of numerical expression." The various units of electrical measurement are next briefly de- scribed. Part II. treats of generators of electricity, commencing with batteries and thermo-electric piles, and running rapidly through most of the best-known machines, This portion of the work, however, is prefaced by a few pages devoted to the generation of induced currents and the laws which govern them ; and this, including a note on the same subject at the end of the book, constitutes the most interesting part of the work, setting forth, as it does, the author's views on the subject of electro-magnetic induction, and more particularly on the complex action of the Gramme ring ; though we believe many electricians are of opinion that its effective action is of a more simple nature, ap- proximating more to that attributed to the Siemens and

Hafner-Alteneck armature. The author, whilst right in point- ing out the great similarity between different machines, is, nevertheless, a little hard on the Wallace-Farmer machine, in describing it as " nothing more than a reproduction on a large scale of Wilde's machine," although, of course, we might go further still, and broadly state that all dynamo - electric machines are constructed on the same principle. Indeed, there appears throughout to be a tendency to severity.on all that is not of Continental origin—which is unfortunate, in a man of Du Moncel's ability. For instance, we read that Brush's machine " much resembles that of De Meritens, though it is less skilfully put together, and reminds me (or us P) of the first attempts made by the last-named gentleman ;" and farther on, " and as with this arrangement, alternately reversed currents are produced, as in De Meritens' machines, and as such currents are unsuitable for the magnetisation of inducing magnets in dynamo-electric machines, it is necessary to put the coils of the revolving ring in communication with a reversing commutator, for which four rubbers are required." This would seem to imply that Mr. Brush had merely adapted the machine of De Meritene, and in order to render such an adaptation possible, had been forced to add a commutator; whereas, we venture to think that Mr. Brush aimed at a high•tension, continuous-current machine for other reasons, his lamp system, for instance. Then follow some interest- ing notes on the efficiency of different machines, principally taken from "the report of the Trinity House on the South Foreland Lighthouse." And here we must protest against the practice of comparing machines by reference to candle-power produced— it is like classing horses according to the number of tons which they can draw, without insuring the conditions being the same, and having, moreover, but indifferent appliances for weighing a ton ! What can be simpler than to state the results in terms of current given against a given resistance P The manufacture and composition of carbons are also briefly described. Part III. contains a description of the earlier forms of arc lamps, and most of the semi-incandescent lamps, though some of the systems which have for some time past found favour in England are passed over or mentioned apologetically ; thus, again, to cite the case of the unfortunate Mr. Brush, " we have considered it our duty to give a description of it [the lamp] here, although it appears to us inferior to those we have in France." To this we would only remark that " the best proof of the pudding is in the eating." The last part of this chapter is devoted to candle lamps, and to that of J'ablochkoff in particular; and here some interesting information is given as to introducing a series of condensers into the lighting circuit—which we do not remember to have seen elsewhere. Part IV. commences with the all-important subject of the cost• of electric lighting. Nothing, perhaps, shows the rapid strides now being taken by the electric light more surely than its reduc- tion in cost. Our author, in stating that the Jablochkoff Com- pany of Paris had undertaken a certain lighting contract in that city at the rate of 30 centimes per lamp per hour, considers that the company will lose thereby. Now, it is interesting to note that the price first paid by the Metropolitan Board of Works for the lighting of the Thames Embankment was 5d. per lamp per hour, it is now lid. Our 'author considers that the figures at present available cannot be considered conclusive, and he is well borne out by Mr. Spottiswoode, in his evidence given before the late Parliamentary Committee, wherein he says, "Nobody knows accurately [what the cost of producing electricity is], and those who might know certainly will not divulge at present." Part V. consists of a few notes on the different applications of the light, which do not call for any particular notice here, and the work ends with two appendices by the translator, the first of which consists of French weights and measures, with their English equivalents, which may possibly have been taken from the fly- leaf of a Letts' diary. The second is on recent inventions, and is meagre in the extreme, three pages only being devoted to incandescent lamps and the Faure accumulator. We think that Mr. Routledge would have done better, had he omitted to mention these interesting novelties altogether ; or, if he con- sidered them to be worth mentioning, to have treated them as they are fairly entitled to be treated.