540 



NATURE 



[October 2, 1890 



of separating the graphite to such an extent that the metal 

 becomes pasty and unfit for making castings. Wonderful, 

 indeed, are the effects of traces of foreign substances on 

 the physical properties of the metals, and, though much 

 has been done towards studying the effect of foreign 

 substances on the properties of iron — the metal of the 

 past, the present, and the future also, notwithstanding all 

 that has been said about aluminium— yet the effects of 

 this new " impurity," aluminium, are so great that evi- 

 dently not only the modern man of science, but also the 

 time-honoured iron-master, has still much to learn. 



H. Baker. 



ELECTRIC DARKNESS. 

 Electric Light : its Production and Use. By John W. 

 Urquhart. Third Edition. (London : Crosby Lock- 

 wood and Son, 1890) 



THIS book has the characteristic defect of many 

 scientific works that go through several editions — 

 the old matter is fondly retained, while edition by edi- 

 tion, new bits of information are inserted here and there, 

 until finally the paragraphs must feel as awkward in one 

 another's company as ancient Britons and gentlemen in 

 top hats. And unfortunately Mr. Urquhart gives no hint 

 to the readers of " Electric Light " as to which are his 

 aboriginal paragraphs painted in woad, and which of 

 them wear the modern frock coat. 



That section of his book which is devoted to arc-lamps 

 almost starts with a description of the latest form of the 

 Brockie-Pell lamp, followed by an account of the Siemens 

 and Hefner Alteneck pendulum and differentiar lamps, 

 the Thomson- Houston, and the Brush lamps, types 

 which may all be met with in constant use at the present 

 day ; then the author, without a word of warning that he 

 is becoming historical, dilates on the Wallace-Farmer 

 and the Rapieff forms. Next comes the Crompton lamp, 

 with only a page given to it, and not thought worthy of 

 an illustration. The reader would hardly gather from 

 this that the Crompton lamp is extensively used in railway 

 stations and elsewhere at home and on the Continent, and 

 that the streets of one of the few towns in England elec- 

 trically lighted — viz., Chelmsford — obtain their light 

 wholly from Crompton lamps. We have then the de- 

 scription of a very excellent lamp, the Pilsen, especially 

 in yiew of the improvements introduced into it by Mr. 

 Joel ; these, however, are not even referred to, Mr. Joel's 

 contribution to electric lighting being confined, according 

 to Mr. Urquhart, solely to his semi-incandescent lamp of 

 1 881. And the description of the Pilsen lamp only occu- 

 pies a fraction of the space devoted to the rotatory disc, 

 the Regnier, the Werdeman, the Wilde, the Jamin blow- 

 pipe lamp, and other obsolete specimens which close this 

 section, wherein may be found some of the most important 

 arc-lamps of the present day indiscriminately jumbled up 

 with types that figure only in museums and text-books. 



Although the book is dated 1890, the description of Sir 

 William Thomson's meters, to which only half a page is 

 given, must have been written several years ago, before 

 Sir William abandoned the use of iron, since, according 

 to "Electric Light," all the assistance Sir William has 

 NO. 1092, VOL- 42] 



contributed to the electric light industry is the invention 

 of a voltmeter in which a stumpy bit of iron is attracted 

 by a coil. The co-inventor of the Ferranti dynamo is 

 we learn, another man, a Sir William Thompson, with 

 a "p." 



With reference to the Deptford mains we are told,. 

 " The main is composed, first, of a copper tube of small 

 diameter surrounded by a considerable thickness of in- 

 sulating material, the whole being enclosed in a copper 

 or other metallic tube about three inches in diameter. 

 It is to be particularly observed that the ' return ' is in- 

 tended to be put in connection with the earth." We 

 should like to hear what the Postmaster-General would 

 say to this bit of intelligence after the opposition that he 

 offered in the spring of 1889 to the original plan being 

 carried out, and which led to the return of the Deptford 

 mains being insulated. 



Details are given of the electric lighting of the Albert 

 Hall by 5 arc-lamps, the author not mentioning that the 

 words, "At the Albert Hall a saving of gas is effected, 

 &c.," and those that follow were written in the very early 

 days of electric lighting. And yet, so anxious to be up 

 to date does the author profess himself to be that he 

 statesj when dealing with high candle-power lamps, " We 

 need not enter more deeply into the question how many,, 

 because . . . calculations made in 1889 would probably 

 not apply in 1890." 



This happy indifference that he displays to the dis- 

 tinction between the past and present tense may very 

 likely lead people to unfairly condemn as useless,. 

 and out of date, a good deal of solid and valuable in- 

 formation which the book contains. The chapter on 

 electric distribution is distinctly good, and the chapters 

 on dynamos may be read with profit if we set down to the 

 author's love of living in the past the accounts he gives 

 of the Wallace-Farmer, of the Biirgin, and of other 

 dynamos now practically abandoned ; and if we attribute 

 to a like cause such information as the following with 

 reference to direct-current dynamos : — "The idea of 

 making the armature a fixture, and of causing the field 

 magnet to revolve within it, has, ... in several lately- 

 constructed machines, proved a most advantageous form 

 of construction." The section on the management of the 

 dynamo is particularly useful, and contrasts most favour- 

 ably with the large amount of historical matter the book 

 contains. We hope, however, that the author's statement 

 regarding a shunt dynamo, as to its probably being im- 

 possible to burn up such a machine by short-circuiting, 

 will not be brought forward as an excuse by some begin- 

 ner for short-circuiting a shunt dynamo which has been 

 running on open circuit ; because the bill that will pro- 

 bably have to be paid for rewinding a burnt-up armature will 

 forcibly illustrate the irnportance of taking into account 

 what the author has neglected, viz. the residual magnetism 

 of the field-magnet cores. 



The detailed instructions which are given for making 

 simple apparatus like batteries, a laboratory magneto 

 Gramme machine, simple arc laiiips, &c., will recom 

 mend the book to amateurs, but the author's views that 

 the vertical slit down the cylindrical zinc of a cell is for 

 the purpose of preventing local action, that " both 

 sides of the zinc evolve electricity," that '-' electricity of 



