April 27, 1893J 



NATURE 



60 ■ 



be blamed for this, but he is |to be blamed for putting 

 forward as a proof in which " there is no speculation," 

 as a '* simple fact, if calculation by figures can be accepted 

 as true," an investigation in which he acknowledges that 

 he estimates this, that, and the other without calculation. 

 v\nd after all, what does he require all this elaborate 

 attempt to cheat nature by complex mechanisms for? 

 Simply because he does not understand fully the position 

 of scientific men in respect of the word " mass," and 

 because he has some d priori difficulties in his own mind 

 as to how atoms of different masses can require equal 

 quantities of heat to warm them through equal ranges 

 of temperature. He says that scientific men say that 

 because a cube of gold weighs seven times as much as a 

 cube of aluminium, " it is therefore taken to comprise 

 seven times the quantity of matter ; ergo it possesses 

 seven times the attractive force, and falls with equal 

 acceleration ; ergo also it requires seven times the force 

 or work to move it." Now this is a gross libel on scien- 

 tific men. That it requires seven times the force to move 

 a cube of gold that is required in the same time to generate 

 the same velocity in an equal cube of aluminium is a 

 matter of experience, and is the only reason why it is 

 said that the mass of the gold is seven times as great as the 

 mass of the aluminium, and this is said because the state- 

 ment is only using the word njass in accordance with the 

 definition of the word. That there is therefoi-e seven 

 times the quantity of matter is really no question of 

 therefore, for the statement is again merely a definition of 

 the term " quantity of matter," which is, in its scientific 

 use, only another name for mass. Now come questions 

 about gravity, and as no satisfactory explanation of 

 gravity {J)ace Le Sage, Tolver Preston, Osborne Reynolds, 

 " Waterdale," and a host of other theorisers upon this 

 interesting subject) has yet been propounded, no scientific 

 person can rightly say that a body attracts seven times as 

 much as another because it has seven times the mass or 

 quantity of matter, for until we know the cause of the 

 attraction we have no right to say that it is because of this 

 or that. Hence there is no therefore at all put forward by 

 scientific men between " seven times the quantity of 

 matter," " or mass," and " seven times as heavy," or " seven 

 times the attractive force." That a body with seven times 

 the mass of another does as a matter of fact weigh seven 

 times as much is a matter of experience, but that it does 

 so because it has seven times the mass is a mere con- 

 jecture, and that it is so held by scientific men is proved 

 by attempts having been made to prove by experiment 

 that weight is proportional to mass, and even to find 

 whether weight varies with the direction of the axis of a 

 crystal, &c. " Waterdale " objects to supposing the ele- 

 mentary atoms bulk for bulk to be of equal density, 

 because " we should have to place the atoms in a light 

 substance too far apart," a fairly good reason for investi- 

 gating the question though not for deciding it. On the 

 other hand he objects to supposing " each atom to be 

 more or less porous — a very incredible hypothesis" — 

 for reasons depending on specific heats to which he 

 evidently attaches some weight, as he harps upon it more 

 than once. Why he should think it so incredible that 

 the atoms may be porous does not clearly appear, for his 

 own atoms,as described in the book, are eminently porous, 

 NO. 1226, VOL. 47] 



and it is upon their porosity that his whole explanation of 

 their behaviour to force, and his application of his prin- 

 ciple of " velocity of force," and his theories of light and 

 electricity and chemical action and adhesion all depend. 

 He would probably reply that he does not want them so 

 porous as all that, though this hardly justifies the epithet 

 " incredible "in respect of a hypothesis he himself holds. 

 Anyway, his serious reason for disbelieving in the unequal 

 masses, or, as he calls it, ponderosities, of atoms is the 

 difficulty he has in seeing how equal quantities of heat 

 can raise unequal masses through equal ranges of 

 temperature. His difficulty rests upon his imagination 

 that he understands fully what the wisest men would 

 probably say they did not understand at all fully, namely, 

 on what property of the atoms of a body temperature 

 depends. He discusses the matter pretty carefully. He 

 says : " How are we to account for the apparent fact that 

 the work of a quantity of heat which is equal to raising 

 weight, I of water i° of temperature — or, in other words, 

 to accelerate, it is to be inferred, the vibrative motion of 

 the whole of its parts in the degree corresponding to one 

 more degree of heat — will be also equal to giving equal 

 acceleration to the entire parts of 8784 and 30'8i6, 

 respectively, more matter in the cases of iron and 

 gold?" He here assumes that equal increments of 

 temperature correspond to equal increments of" accelera- 

 tion " of the atoms. This, if it means anything, is not 

 true, and it is not a priori at all likely. Take another 

 place, where he says, " . . . . The fact that a given 

 quantity of imparted heat raised a really heavy atom to 

 the same temperature as it would a really lighter atom, 

 would indicate that equal temperatures were marked by 

 a slow motion of heavy wedges in respect of a heavy 

 atom, and by a quick motion of light wedges in respect 

 to light atoms." 



" Although the same quantity of heat might thus be im- 

 parted to the two atoms, it is reasonable to infer that the 

 intensity of the heat, as made apparent to our senses, would 

 not in the two cases be identical." "... It is reason- 

 able to infer," on the other hand, that there is some hitch 

 in an argument that depends to any important degree 

 upon such a form of expression as " it is reasonable to 

 infer." Is it not, on the other hand, most reasonable to 

 infer that the blow given by a light body moving quickly 

 would be very much the same as by a heavy body moving 

 more slowly, and that, consequently, the " intensity of 

 heat," as he calls it, would feel the same ? In any case 

 a very cursory study of the kinetic theory of gases 

 would point out how there is certainly no incongruity or 

 incredibility, but quite the reverse, in the notion that 

 equal quantities of heat do make light atoms move rapidly 

 and heavy ones slowly ; and that, notwithstanding their 

 different atomic velocities, the temperatures of two bodies 

 may be the same. There is no real difficulty in sup- 

 posing that it requires thirty times as much heat to raise 

 the temperature of water as is required to raise an 

 equal mass of gold through the same range of tempera- 

 ture, if we bear clearly in mind the very complex struc- 

 ture of both water and gold, and all that has to be done 

 by the heat in each case, and at the same time recollect 

 how very little we know of the conditions that determine 

 when two bodies are at the same temperature, i.e. that 



