304 



NA TURE 



\Atig. 20, 1874 



It is wonh while, however, to take note of the progress 

 of evolution by which the words of ordinary language are 

 gradually becoming differentiated and rendered scienti- 

 fically precise. The fathers of dynamical science found 

 a number of words in common use expressive of action 

 and the results of action, such as force, power, action, 

 impulse, impetus, stress, strain, work, energy, &c. They 

 also had in their minds a number of ideas to be expressed, 

 and they appropriated these words as they best could to 

 express these ideas. But the equivalent words Force, Vis, 

 Kraft, came most easily to hand, so that we find them 

 compelled to carry almost all the ideas above mentioned, 

 while the other words which might have borne a portion 

 of the load were long left out of scientific language, and 

 retained only their more or less vague meanings as ordi- 

 nary words. 



Thus we have the expressions Vis accclerairix. Vis 

 motrix, Vis viva, Vis moiiua, and even Vis inertia:, in 

 every one of which, except the second and fourth, the 

 word Vis is used in a sense radically different from that 

 in which it is used in the other expressions. 



Confusion may perhaps be avoided in scientific works 

 when read by scientific students, by means of a careful 

 appropriation of epithets such as those which distinguish 

 the meanings of the word 17^, but as soon as science 

 becomes popularised, unless its nomenclature is reformed 

 and arranged upon a better prinniole, the ideas of popular 

 science will be more confused tlian those of so-called 

 popular ignorance. 



Thus the "Phjsical Forces," whose correlation is dis- 

 cussed in the essay before us, are Motion, Heat, Elec- 

 tricity, Light, Magnetism, Chemical Affinity, and " other 

 modes cf force." According to the definition of force, as 

 it has been laid down during the last two centuries in 

 treatises on dynamics, not one of these, except perhaps 

 chemical affinity, can be admitted as a force. According 

 to that definition, " force is that which produces change 

 of motion, and is measured by the change of motion 

 produced." 



Newton himself reminds us that force exists only so 

 long as it acts. Its effects may remain, but the force 

 itself is essentially transitive. Hence, when we meet with 

 such phrases as Conservation of Force, Persistence of 

 Force, and the like, we must suppose the word Force to be 

 used in a sense radically different from that adopted by 

 scitntific men from Newton downwards. In all these 

 cases, and in the phrase "The Physical Forces" as ap- 

 plied to heat, we are now, thanks to Dr. Thomas Young, 

 able to use the word Energy instead of Force, for this word, 

 according to its scientific definition as " the capacity for 

 ■f.crf irmii'g wor!;," is applicable to all thrse cases. The 

 confusion has extended even 10 the metaphorical use of 

 the word Force. Thus, it may be a legitimate metaphor 

 to speak of the force of public opinion as being broujjht 

 to bear on a statesman so as to exert an overpowering 

 pressure upon him, because here we have an action tend- 

 mg to produce motion in a particular direction ; but 

 when we speak of " the Queen's Forces,"' we use the term 

 in a sense as unscientific as when we speak of the 

 Physical Forces. The author, in his concluding remarks, 

 p'^inls out the confusion ol terms which emb.irrassed him 

 i.i i>'b eiiii';..vours to enunciate scientific propositions, on 

 . -cuiuol the imperfection of scientific language. liiis, 



he tells us, " cannot be avoided without a neology which 

 [ have not the presumption to introduce or the authority 

 to enforce." 



Such a confession, proceeding from so great a master of 

 the art of "putting things," is a most valuable testimony to 

 the importance of the studyand special cultivation of scien- 

 tific language ; and a comparison of many passages in the 

 essay with the corresponding statements in more recent 

 books of far inferior power, will show how much may be 

 gained by the successful introduction of appropriate 

 neologies. What appeared mysterious and even para- 

 doxical to the giant, labouring among rough-hewn words, 

 dwindles into a truism in the eyes of the child, born heir 

 to the palace of truth, for the erection of whic'n the giant 

 has furnished the materials. 



Thus the appropriation of the word " Mass " to denote 

 the quantity of matter as defined by the amount of force 

 required to produce a given acceleration, has placed the 

 students of the present day on a very different level from 

 those who had to puzzle out the meaning of the phrase 

 Vis Inert i(c by combining the explanation of Vis as force, 

 with that of Inertia as laziness. In the same way the 

 word " stress " as an equivalent for " action and reaction," 

 and as a generic name for pressure, tension, &c., will save 

 future generations a great deal of trouble ; and the dis- 

 tinction between the possession of energy and the act of 

 doing work, which is now so familiar to us, would have 

 obviated several objections to the doctrine of the essay, 

 which are founded on statements in which the production 

 of one form of energy and the maintenance of another 

 are treated as if they were operations of the same kind. 

 We read at p. 163 : — Thus, " a voltaic battery, decompos- 

 ing water in a voltameter, while the same current is em- 

 ployed at the same time to make (maintain) an electro- 

 magnet, gives nevertheless in the voltameter an equivalent 

 of gas, or decomposes an equivalent of an electrolyte for 

 each equivalent of decomposition in the battery cells, and 

 will give the same ratios if the electro-magnet be removed." 

 Here the maintenance of a magnet is a thing of a 

 different order from the decomposition of an electrolyte ; 

 the first is maintenance of energy, the other is doing work. 

 This is well explained in the essay ; but if appropriate 

 language had been used from the first, the objection could 

 never have been put into form. 



J. C. Clerk-Maxwell. 



FIRST FORMS OF VEGETATION 

 First Forms of Vei;etation. By the Rev. Hugh Mac- 

 raillan, LL.D. Second edition, corrected and revised. 

 (London : Macmillan and Co.) 



DR. MACMILLAN explicitly informs his readers in 

 his preface to his book, that his object is not so 

 much to impart cut-and-dried information as to kindle 

 their sympathy and awaken their interest " in a depart- 

 ment of nature with which few, owing to the technical 

 phraseology of botanical works, are familiar." Such a 

 purpose is very laudable indeed, and the book which 

 carried it into effect might have been a very valuable one. 

 Science has great need of evangelists. Students of its 

 various branches experience the keenest interest in follow- 

 ing up the lines of research and investigating the problems 

 which belong to their own departments. But to feel this 



