SPECULATIVE SCIENCE. 157 



to the authors of "The Unseen Universe " to follow out the consequences of this 

 statement. 



I may safely take it for granted after this, I presume, that, while 

 Professor Newcomb may have a vocation for expounding and defend- 

 ing the kinetic theory of gases, he has no special call, as he supposes, 

 to stand up for Clerk Maxwell and his opinions. 



It is hardly necessary to say that Professor Newcomb does not 

 honor my objections to the kinetic theory of gases with any notice or 

 attempt at refutation. He observes that " an abstract of them is im- 

 possible," which is to be regretted, for, if he had undertaken to give 

 us one, we should undoubtedly have learned some noteworthy things. 

 The task of making such an abstract does not appear to be very dif- 

 ficult. What I insist on is, that every valid physical theory is essen- 

 tially a simplification and not a complication, a reduction of the number 

 of unrelated facts which it undertakes to account for, and not a mere 

 substitution of many arbitrary assumptions of unknown and unverifiable 

 facts for a few known facts that is to say, speaking in the language 

 of mathematics, that every true physical theory is in effect a reduction 

 of the number of independent variables representing the phenomena 

 to be explained. And I show that the kinetic theory of gases not only 

 fails to satisfy this requirement, but is a complete reversal of a legiti- 

 mate scientific procedure. This is the sense of the passage which Pro- 

 fessor Newcomb parades before the unwary reader, whom he ought to 

 have shocked still more with my horrible suggestion (which I now 

 deliberately repeat) that a gas is in its nature a simpler thing than a 

 solid, and that no attempt to account for its properties by taking those 

 of a solid as a basis and making arbitrary additions to them is likely 

 ever to succeed. 



It is not a little instructive to note the character of sacredness as- 

 cribed by persons of Professor Newcomb's frame of mind to dominant 

 physical theories, and the violence with which they repel every attempt 

 to point out their defects. My reviewer in " The Critic " is almost be- 

 side himself after reading my " assault " on " that magnificent fabric 

 of science, the undulatory theory of light and heat." Before he pelts 

 me again with his missiles, he will do well to look and see who is 

 standing at the place to which he directs them. There is at Harvard 

 University a most learned and laborious scientist whose merits as an 

 original investigator are at least equal, if not superior, to his inestima- 

 ble services as an expounder of scientific truth, and the extent of whose 

 attainments is no less conspicuous in his memoirs and books than the 

 clearness of his intellect Professor Josiah P. Cooke, Jr. In May, 

 1878, Professor Cooke published a lecture on the radiometer in this 

 journal (' f Popular Science Monthly "), in which he had occasion to 

 speak of the undulatory theory of light and the luminiferous ether. 

 And there (pages 11, 12) we find this language : 



But turn now to tl^e astronomers, and learn what they have to tell us in re- 



