266 



NATURE 



\yuly 21, 1887 



lurgy of the precious metals. Such results will probably 

 not be realized in their entirety, neither is it desirable 

 that they should be, as the presence of a well-educated 

 specialist, an assayer or smelter, for example, may often be 

 of more permanent value to a district than the necessarily 

 superficial knowledge of subjects not immediately con- 

 nected with their own occupation that the local miners are 

 likely to acquire under the scheme ; but there can be no 

 doubt that great good will result from giving them an intel- 

 ligent interest in mineralogy, and the observation of the 

 phenomena brought under their notice when at their own 

 particular work. 



The Hand-book concludes with a description of the 

 principal forest trees of New Zealand, taken from Dr. 

 Hector's " Hand-book of New Zealand." It has also 

 several maps, supplied by Dr. Hector and Mr. Gordon, of 

 the Mines Department. The greater part of the material 

 has been collected by Mr. Patrick Galvin, of Wellington. 



We are sorry to see that in the final paragraphs of the 

 preface, Mr. Larnach appeals to the honourable gentle- 

 man who may succeed him to improve the work in a 

 second edition ; from which we infer that the author has 

 fallen a victim to a Ministerial crisis. If it be so, we have 

 to thank him for what he has done, but if not, we hope 

 that he may have the opportunity of extending and im- 

 proving the work which he has so worthily begun, instead 

 of leaving it to his successor. H. B. 



A CENTURY OF ELECTRICITY. 



A Century of Electricity. By T. C. Mendenhall. (London: 

 Macmillan and Co., 1887.) 



IN this readable little work. Prof. Mendenhall has 

 striven to depict the origin and growth of many of 

 the modern electric appliances — the telegraph, the 

 dynamo, the telephone, and the electric lamp. He opens 

 with a felicitous quotation from Benjamin Franklin 

 describing with characteristic humour a proposal to hold 

 an electrical party of pleasure on the banks of the 

 Skuylkil, when the healths of all the famous electricians 

 in England, Holland, France, and Germany are to be 

 " drank " in electrified bumpers, under the discharge of 

 guns from the electrical battery. This is followed by a 

 very interesting account of the early development of the 

 experimental science, and in particular of the work of 

 Gilbert and of Franklin. It is satisfactory to note that 

 for once Gilbert's just fame as the creator of the double 

 science of electricity and magnetism is recognized, and 

 his pre-Baconian use and development of the experi- 

 mental and deductive methods of philosophizing acknow- 

 ledged. The discoveries of Galvani, Volta, Oersted, and 

 Ampere are set forth in a style which, while losing 

 nothing in accuracy of description, is enlivened by pleasant 

 biographical touches. Speaking of the week during 

 which Ampere wrought out to such brilliant conclusions 

 the train of ideas suggested by Oersted's discovery of the 

 electric deflexion of the magnet. Prof. Mendenhall ob- 

 serves ; " It is safe to say that the science has at no other 

 time advanced with such tremendous strides as during 

 that memorable week." The work of Sturgeon in invent- 

 ing, and of Henry in perfecting, the electro-magnet is duly 

 noted ; but we miss, in connexion with electro-magnetic 



subjects^ the name of Prof. Gumming, who did so much 

 to expand and define the growing science. 



The vexed question. Who invented the electric tele- 

 graph ? is here reached, and is very carefully handled. Prof. 

 Mendenhall's frank impartiality in touching on this and 

 sundry other delicate topics of contested priority is worthy 

 of praise. A propos of the part taken by Henry in the 

 invention of the electric telegraph, the author gives a sketch 

 of Henry's arrangement of a bell for receiving electric 

 signals, with a polarized lever to strike the bell, as it was 

 exhibited in Albany in 1832. The most technical part of 

 the work is that dealing with duplex and multiplex tele- 

 graphy, which is very fully treated, though here we miss 

 the name of La Cour, who preceded Delany in the syn- 

 chronous distribution of currents. Sir William Thomson's 

 labours in submarine telegraphy, and those of Gaston 

 Plants on accumulators, are emphasized, but not unduly. 

 Respecting the telephone, after noting the early work of 

 Page and the similarity between Reis's telephone trans- 

 mitter and those used to-day, the author turns to the 

 work of Elisha Gray and Graham Bell in the following 

 terms : — " By a curious coincidence Mr. Gray deposited his 

 specifications and drawings for a speaking-telephone in the 

 United States Patent Office, in the form of a caveat, on 

 February 14, 1876; and on the same day Mr. Bell filed 

 his application for a patent, the latter being received a 

 few hours earlier than the former. The coincidence be- 

 comes more interesting when it is remembered that it 

 was also on February 14, 1867, that Wheatstone and 

 Siemens simultaneously presented to the Royal Society 

 their independent discovery of the important fact that 

 dynamo-electric machines could be constructed and 

 operated without the use of permanent magnets." The 

 double coincidence of dates is certainly curious ; but the 

 significance of it is marred when we remember, first, that 

 both Wheatstone and Siemens must yield priority of date 

 to Varley,who patented the same discovery on December 

 24,1866; and,secondly,thattheapparatusdescribedbyBell 

 in the patent application of February 14, 1876, was one 

 in which a separate instrument was employed for every 

 pitch, " each instrument being capable of transmitting or 

 receiving but a single note," and therefore did not 

 describe a speaking-telephone at all. Bell's patent for 

 "the transmission by the same means of articulate 

 speech " was only applied for some ten months later. 

 Due credit is given to Hughes for his well-known research 

 on the microphone, to Edison for his button of lamp- 

 black, and to Dolbear for the invention of the electro- 

 static receiver. The chapter on the electric light is all 

 too short, and might with advantage be expanded. 

 Faraday's splendid discovery of magneto-electric induc- 

 tion, leading to the invention of the dynamo, is admirably 

 recounted, and the important part played by modern 

 American constructors of powerful machines is modestly 

 narrated. A similar remark will apply to the paragraphs 

 upon electric motors, a department of electro-technics 

 which America is likely to make peculiarly her own. 



When we reflect that the rapid introduction into 

 British industries of the gas-engine is slow compared 

 with the tremendous rate at which electric motors are 

 being everywhere brought into use in the States, we think 

 that Prof. Mendenhall has under-rated rather than over- 

 rated the importance of this item in his account of the 



