THE HISTORY OF A DOCTRINE. 393 



I had been trained in the orthodox scientific church, of which 

 I am happy to be still a member ; but I had acquired perhaps an 

 almost undue respect, not only for her dogmas, but for her least 

 sayings. Accordingly, when my own experiments did not agree 

 with the received statement, I concluded that my experiments 

 must be wrong, and made them all over again, till spring, sum- 

 mer, autumn, and winter had passed, each season giving its own 

 testimony ; and this for successive years. The final conclusion 

 was irresistible, that the universal statement of this alleged well- 

 known fact (inexplicable as this might seem, in so simple a mat- 

 ter) was directly contradicted by experiment. 



I had some natural curiosity to find how every one knew this 

 to be a fact ; but search only showed the same statement (that 

 the earth's atmosphere absorbed dark heat like glass) repeated 

 everywhere, with absolutely nowhere any observation or evidence 

 whatever to prove it, but each writer quoting from an earlier one, 

 till I was almost ready to believe it a dogma superior to reason, 

 and resting on the well-known " Quod semper, quod ubique, quod 

 ah omnibus, creditum est." 



Finally, I appear to have found its source in the writings of 

 Fourier, who, alluding to De Saussure's experiments (which 

 showed that dark heat passed with comparative difficulty through 

 glass), observes that, if the earth's atmosphere were solid, it would 

 act as the glass does. Fourier simply takes this (in which he is 

 wholly wrong) for granted ; but as he is an authority on the 

 theory of heat, his words are repeated without criticism, first by 

 Poisson, then by others, and then in the text-books; and, the 

 statement gaining weight by age, it comes to be believed abso- 

 lutely, on no evidence whatever, for the next sixty years, that our 

 atmosphere is a powerful absorber of precisely those rays which 

 it most freely transmits. 



The question of fact here, though important, is, I think, quite 

 secondary to the query it raises as to the possible unsuspected in- 

 fluence of mere tradition in science, when we do not recognize it 

 as such. Now, the Roman Church is doubtless quite logical in 

 believing in traditions, if these are recommended to the faithful 

 by an infallible guide ; but are we, who have no infallible guide, 

 quite safe in believing all we do, with our fond persuasion that in 

 the scientific body mere tradition has no weight ? 



In even this brief sketch of the growth of the doctrine of ra- 

 diant energy, we have perhaps seen that the history of the prog- 

 ress of this department of science is little else than a chapter in 

 that larger history of human error which is still to be written, 

 and which, it is safe to say, would include illustrations from other 

 branches of science as well as my own. 



But — and here I ask pardon if I speak of myself — I have been 



