May 8, 1884] 



NA TURE 



27 



Prof. Carey Foster, Prof. Hughes, Prof. Fleeming-Jcnkin, 

 Mr. Graves, and Mr. Preece. The full text of the resolu- 

 tions is as follows : — 



" I. Electric Units, strictly so called. First Resolution : 

 The legal ohm is the resistance of a column of mercury of 

 a square millimetre cross-section and 106 centimetres in 

 length at the temperature of melting ice. Second Resolu- 

 tion : The Conference expresses the wish that the French 

 Government should transmit this resolution to the dif- 

 ferent States, and recommend an international adoption 

 of it. Third Resolution : The Conference recommends 

 the construction of primary standards in mercury con- 

 formable to the resolution previously adopted, and the 

 concurrent employment of scales of secondary resistances 

 in solid alloys which shall be frequently compared 

 amongst one another and with the primary standard. 

 Fourth Resolution : The ampere is the current the abso- 

 lute value of which is ten to the power minus one in 

 electro-magnetic units. Fifth Resolution : The volt is the 

 electromotive force which maintains a current of one 

 ampere in a conductor the resistance of which is one legal 

 ohm. 



" II. Earth-Currents and Lightning-Rods. First Reso- 

 lution: It is to be desired that the results of observations 

 : collected by the various administrations be sent each year 

 j to the International Bureau of Telegraph Administration 

 I at Berne, which will make a digest of them and communi- 

 cate it to the various Governments. Second Resolution : 

 The Conference expresses the wish that observations of 

 earth-currents be pursued in all countries. 



"III. Standard of Light. Resolution : The unit of each 

 kind of simple light is the quantity of light of the same 

 kind emitted in a normal direction by a square centimetre 

 of surface of molten platinum at the temperature of 

 solidification. The practical unit of white light is the 

 j quantity of light emitted normally by the same source." 

 j 



DR. JOULE'S SCIENTIFIC PAPERS 

 The Scientific Papers of James Preseott Joule, D.C.L., 

 LL.D., F.R.S., tec. (London : Published by the 

 Physical Society, 1884.) 

 1 /^\UR benefactors are oftentimes unrecognised! The 

 ! ^J writer of the present notice of our latest ac- 

 quisition in scientific literature, takes credit to himself 

 for having been the first to propose to Sir William 

 Thomson the reprinting of his original papers. Seized 

 with a great desire to possess those invaluable electro- 

 static papers, which, in 1867, could only be read in the 

 original by those who were fortunate enough to have 

 I access to the Cambridge and Dublin Mathematical 

 j Journal, he urged that there must be many others by 

 I whom a reprint would be gladly welcomed. Thus was 

 originated the reprint of the " Electrostatics and Mag- 

 netism." 



The initiative being taken, we have now a second series 

 from Sir William Thomson — part published, part in pro- 

 gress — intended to include all his mathematical and 

 physical papers. Prof. Stokes also, under the influence 

 of pressure and good example, has produced the first half 

 of a reprint of his classical papers. Abroad we have col- 

 lections of the papers of Prof, von Helmholtz and Prof. 

 Kirchoff. Last at the present moment, but far from the 



least in importance or in general interest, we have the 

 first volume of republished papers by Mr. Joule. 



But what a debt of gratitude we owe to the Physical 

 Society for its publishing enterprise— first for the publica- 

 tion of Prof. Everett's " Illustrations of the C.G.S. System," 

 a book which has been helpful to every student of physical 

 science ; then for its graceful tribute to the memory of 

 Wheatstone ; and now for this fresh and most happy 

 undertaking. 



Before looking at the papers themselves, let us unburden 

 ourselves of one or two remarks. The form of the book 

 is admirable. The printing and the diagrams are all that 

 can be desired. The accuracy of the author of the papers, 

 who has personally undertaken the editing, appears in 

 that there is scarcely a misprint to be found in the 650 

 pages. One serious want, and one only, we have felt, 

 and it is this. Throughout the book there are many back 

 references to previous papers. These references are 

 given in footnotes exactly as they were given in the 

 original papers, thus, Phil. Mag., ser. 3, vol. xiii. p. 268. 

 But what the reader of the book wants, nay absolutely 

 requires, is the reference to the page of the reprint itself 

 where the passage alluded to is to be found. May we be 

 allowed to suggest this as an improvement for the second 

 volume now promised ? 



To come to the papers themselves, almost one hundred 

 in number. There is a considerable number of unconnected 

 papers on a great variety of subjects, several on meteoro- 

 logical phenomena, six or eight on new instruments or 

 modifications of instruments, a mercurial pump, an 

 improved barometer, a new dip circle, a current meter, 

 &c, in addition to his tangent galvanometer, and one or 

 two others to which we will immediately refer more parti- 

 cularly ; then we have a paper on utilisation of sewage ; a 

 note on the prevalence of hydrophobia ; improvements in 

 the common kite, &c. : all of considerable value. For the 

 most part, however, the papers are on two or three classes 

 of subjects very closely connected, and these are of super- 

 lative interest, containing, as they do, the germs, or rather 

 affording the foundation, of the modern theory of energy-. 



Mr. Joule's papers are remarkable in form as well as in 

 substance. Of mathematics there is scarcely a line : but 

 what clearness, and depth, and penetration into the 

 hidden things of Nature ! Thus their interest is general 

 to an unusual degree. To those who shun the labour of 

 arriving at results by "chasing the p" through mazes of 

 equations they are the perfection of clear exposition of 

 fundamental principles. The mathematician, on the 

 other hand, finds in them a model of concise expression, 

 and results of experimental investigation stated in a form 

 ready and convenient for being represented in mathe- 

 matical symbols. 



It is impossible within the limits to which these lines 

 are necessarily confined to notice exhaustively the investi- 

 gations themselves, or even the results arrived at. We 

 must content ourselves with a brief reference to some of 

 the most important. 



The first subject which seems to have attracted the 

 attention of Mr. Joule was that of magnetism and the 

 electro-magnetic engine. His earliest papers are taken 

 up with the description of novel forms of the electro- 

 magnetic engine, and of experiments in this connection. 

 In a very early paper he investigates the laws relating to 



