442 



NATURE 



[March 12, 1896 



Reymond is not infallible, and most prophecies as to the 

 limits of human knowledge have turned out to be only 

 limits to the ingenuity of the prophet. It is very much 

 more likely that Du Bois Reymond's apparently resistless 

 logic has a flaw, than that the path of progress of science 

 for three hundred years has been along the wrong route. 

 There are plenty of philosophical speculations, which no 

 doubt Du Bois Reymond brushes aside as hardly worth 

 consideration, which would entirely invalidate the greater 

 part of his arguments. Even though they do not, it is 

 certainly quite unscientific to leave a road that has led to 

 great discoveries merely because you imagine that there 

 is some curious spectre in the distance to which you think 

 it is leading you. 



Prof. Ostwald's fourth attack is based on the fact that 

 seeds grow into trees, but that trees do not grow back 

 again into seeds. He thinks that if the universe were a 

 mechanical system, there is no more reason for one than 

 the other, and that they should occur equally often. As 

 he says, "the tree could return again to the sapling, 

 &c." But that is not the question. The question is, must 

 it, if this is a mechanical universe. The order of events 

 depends entirely, in a mechanical universe, upon the 

 initial conditions^ and all we can say is that the initial 

 conditions of this earth were such that trees generally 

 grow from seeds, and that the reverse operation has never 

 been known to occur. That it has never occurred has 

 nothing on earth to say to the question of whether this 

 is a mechanical universe. As a matter of fact, I believe 

 that this and other much simpler cases, such as are 

 usually classed under irreversible actions in thermo- 

 dynamics, can be shown to be not only, as I have 

 here argued, possible mechanical processes, but to be 

 the most probable mechanical processes. Hence it is 

 quite possible that the actual sequence of events which 

 Prof Ostwald cites as disproving the mechanical theory 

 of the universe may be the very best proof extant, not 

 only that the mechanical theory is the most probable 



from those dreadful hypotheses. He prefers volume 

 energy to the molecular theory of gases. He criticises 

 this latter by neglecting to see that the quantity often 

 quoted as energy per cubic centimetre of the gas is 

 really momentum per second carried across a plane, and 

 has consequently that very element of direction which 

 he accuses it of not possessing, and the absence of 

 which in volume energy one might possibly expect him 

 to explain. Prof. Ostwald's idea of science as free from 

 hypothesis is the most advanced form of pure positivfsm. 

 If he were consistent, he should deny the existence of 

 thought in the moving coloured, soft, objects he sees 

 and feels around him, and calls men. That other men 

 think is a hypothesis ; and if he rejects all hypotheses, 

 why not this ? 



In conclusion. Prof Ostwald seems to have some dim 

 doubt whether energetics will explain everything. As 

 the doctrine of the conservation of energy will not deter- 

 mine by itself the motion of even a single planet round 

 the sun, it is somewhat curious to see the doubt that 

 seems to haunt him in answering this question. The 

 doctrine of the conservation of energy is most valuable, 

 but it goes only a very little way in explaining pheno- 

 mena. More than energetics is certainly required unless 

 we are prepared to endow energy with all sorts of curious 

 properties after the manner of our predecessors, who 

 used to invent a new subtle fluid with convenient proper- 

 ties in order to explain every new difficulty. Prof. 

 Ostwald's energy seems more like one of these subtle 

 fluids than any product of modern thought. 



Geo. Fras. Fitzgerald. 



THE HIGHLANDS OF PERU. ' 

 HE two first volumes of this work were noticed in 

 Nature, vol. li. p. 388. and the general remarks 

 made there apply in great measure to the new volume 

 also. We must, however, observe that the highlands of 



T 



The Andes from Chililaya, Lake Titicaca 



theory, but it may even lead us to conclude that it is the 

 only possible theory. 



Finally, Prof Ostwald tries to build up something 

 instead of what he thinks he has demolished. A vague 

 energetics is what he presents instead of the mechanics 

 of the past. He advocates the deadly view that science 

 should be a catalogue, well arranged, no doubt, but free 



NO. 1376, VOL. 53] 



Peru afford material for a much more interesting descrip- 

 tion than the coast and the capital, which were dealt with 

 in somewhat wearisome detail. Here the narrative form 

 is not unwelcome, for there is always a charm in the 



1 " Beobachtungen und Studien fiber das Land und seine Bewohnfer 

 wahrend eines 25-jahrigen Aufenthalts." IIL Band. Das Hochland von 

 Peru. Von E. W. Middendorf. Pp. 604. (Berlin : Robert Oppenheim [Gustav 

 Schmidt], 1895.) 



