392 SCIENCE PROGRESS 



ably expect a physicist to " feel " that there is a bright spot at 

 the centre of a circular shadow, that glass is a better conductor 

 of some kinds of electric currents than copper, that a surface 

 of separation between two perfectly transparent media is a 

 better reflector than polished opaque silver? Would any 

 chemist have those "stirrings in the viscera" — as Professor 

 James put it — which would lead him to expect that " inert " 

 nitrogen could exist in a most active allotropic modification; 

 or that, in spite of all that had been said about the cause of the 

 activity of substances in a " nascent " condition, the new mon- 

 atomic gases should be totally inert ? We know that there were 

 chemists who flatly contradicted the truth of the last example 

 and that solely on the evidence of their feelings. As a last 

 example we might take the question of the constitution of isatin, 

 which had been settled agreeably to the feelings of chemists 

 until Hartley and Dobbie showed that the actual facts were 

 exactly the opposite to what we should expect. It is undoubt- 

 edly true that chemists have made instinctive guesses which 

 have later on been shown to be quite incorrect. Some of the 

 guesses are bound to turn out right in any case on the theory 

 of probabilities but this is no justification for the use of guess- 

 work as a scientific method ; if scientists denied any validity to 

 the principle of the Discrimination of the Unscientific Instinct 

 in the time of Darwin, how can they defend their own use of 

 an identical principle now ? 



When we come to deal with the three pedagogic questions, 

 we find that Mr. Worley has spared us the trouble of discussing 

 the first, for his paper leaves no doubt remaining that he recog- 

 nises the great value, both from a practical and from an 

 educational standpoint, which a mathematical education has 

 for a chemist. 



In dealing with the second and third problems he is less 

 clear than could be wished. It is, of course, necessary to 

 make up our minds at the start not only what we are going 

 to teach but who is to be taught; the initial knowledge and 

 the future prospects of the student must always regulate the 

 course of any teaching that is going to be fair and straight- 

 forward, not merely the result of faddism or slavish adherence 

 to some pet educational doctrine. I wish to make it clear at 

 this point that I am not thinking, in referring to "the future 

 prospects " of the student, of his ultimately competing in any 



