BODILY ILLNESS AS A MENTAL STIMULANT. 243 



An even more curious instance of a mistake arising 

 from doing one thing while thinking of another occurred 

 to me fourteen years ago. I was correcting the proof- 

 sheets of an astronomical treatise in which occurred these 

 words : * Calling the mean distance of the earth i, Saturn's 

 mean distance is 9*539 ; again, calling the earth's period i, 

 Saturn's mean period is 29*457 : now what relation exists 

 between these numbers 9*539 and 29*457 and their powers? 

 The first is less than the second, but the square of the first 

 is plainly greater than the second we must therefore try 

 higher powers, &c. &c.' The passage was quite correct as 

 it stood, and if the two processes by which I was correct- 

 ing verbal errors and following the sense of the passage had 

 been really continuous processes of thought, unquestionably 

 the passage would have been left alone. If the passage had 

 been erroneous and had been simply left in that condition 

 the case would have been one only too familiar to those 

 who have had occasion to correct proofs. But what I 

 actually did was deliberately to make nonsense of the pas- 

 sage while improving the sound of the' second sentence. 

 I made it run, * the first is less than the second, but the 

 square of the first is plainly greater than the square of the 

 second,' the absurdity of which statement a child would 

 detect. If the first proof in its correct form, with the in- 

 correct correction carefully written down in the margin, had 

 not existed when, several months later, the error was pointed 

 out in the Quarterly Journal of Science, I should have 

 felt sure that I had written the words wrongly at the 

 outset. For blunders such as this are common enough. 

 But that I should deliberately have taken a correctly 

 worded sentence and altered it into utter absurdity I could 

 not, but for the evidence, have believed to be possible. The 

 case plainly shows that not only may two things be done at 

 once when the mind, nevertheless, is thinking only of one, 

 but that something may be done which suggests deliberate 

 reflection when in reality the mind is elsewhere or not occu- 

 pied at all. For in this case both the processes on which 



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