This Postscript puzzled me sorely. ‘He is far too sensible a man,’ I thought, ‘to have become a Fatalist. And yet what else can he mean by it?’ And, as I folded up the letter and put it away, I inadvertently repeated the words aloud. ‘Do you believe in Fate?’

      The fair ‘Incognita’ turned her head quickly at the sudden question. ‘No, I don’t!’ she said with a smile. ‘Do you?’

      ‘I—I didn’t mean to ask the question!’ I stammered, a little taken aback at having begun a conversation in so unconventional a fashion.

      The lady’s smile became a laugh—not a mocking laugh, but the laugh of a happy child who is perfectly at her ease. ‘Didn’t you?’ she said. ‘Then it was a case of what you Doctors call “unconscious cerebration”?’

      ‘I am no Doctor,’ I replied. ‘Do I look so like one? Or what makes you think it?’

      She pointed to the book I had been reading, which was so lying that its title, ‘Diseases of the Heart,’ was plainly visible.

      ‘One needn’t be a Doctor,’ I said, ‘to take an interest in medical books. There’s another class of readers, who are yet more deeply interested—’

      ‘You mean the Patients?’ she interrupted, while a look of tender pity gave new sweetness to her face. ‘But,’ with an evident wish to avoid a possibly painful topic, ‘one needn’t be either, to take an interest in books of Science. Which contain the greatest amount of Science, do you think, the books, or the minds?’

      ‘Rather a profound question for a lady!’ I said to myself, holding, with the conceit so natural to Man, that Woman’s intellect is essentially shallow. And I considered a minute before replying. ‘If you mean living minds, I don’t think it’s possible to decide. There is so much written Science that no living person has ever read: and there is so much thought-out Science that hasn’t yet been written. But, if you mean the whole human race, then I think the minds have it: everything, recorded in books, must have once been in some mind, you know.’

      ‘Isn’t that rather like one of the Rules in Algebra?’ my Lady enquired. (‘Algebra too!’ I thought with increasing wonder.) ‘I mean, if we consider thoughts as factors, may we not say that the Least Common Multiple of all the minds contains that of all the books; but not the other way?’

      ‘Certainly we may!’ I replied, delighted with the illustration. ‘And what a grand thing it would be,’ I went on dreamily, thinking aloud rather than talking, ‘if we could only apply that Rule to books! You know, in finding the Least Common Multiple, we strike out a quantity wherever it occurs, except in the term where it is raised to its highest power. So we should have to erase every recorded thought, except in the sentence where it is expressed with the greatest intensity.’

      My Lady laughed merrily. ‘Some books would be reduced to blank paper, I’m afraid!’ she said.

      ‘They would. Most libraries would be terribly diminished in bulk. But just think what they would gain in quality!’

      ‘When will it be done?’ she eagerly asked. ‘If there’s any chance of it in my time, I think I’ll leave off reading, and wait for it!’

      ‘Well, perhaps in another thousand years or so—’

      ‘Then there’s no use waiting!’ said my Lady. ‘Let’s sit down. Uggug, my pet, come and sit by me!’

      ‘Anywhere but by me!’ growled the Sub-Warden. ‘The little wretch always manages to upset his coffee!’

      I guessed at once (as perhaps the reader will also have guessed, if, like myself, he is very clever at drawing conclusions) that my Lady was the Sub-Warden’s wife, and that Uggug (a hideous fat boy, about the same age as Sylvie, with the expression of a prize-pig) was their son. Sylvie and Bruno, with the Lord Chancellor, made up a party of seven.

      ‘And you actually got a plunge-bath every morning?’ said the Sub-Warden, seemingly in continuation of a conversation with the Professor. ‘Even at the little roadside-inns?’

      ‘Oh, certainly, certainly!’ the Professor replied with a smile on his jolly face. ‘Allow me to explain. It is, in fact, a very simple problem in Hydrodynamics. (That means a combination of Water and Strength.) If we take a plunge-bath, and a man of great strength (such as myself) about to plunge into it, we have a perfect example of this science. I am bound to admit,’ the Professor continued, in a lower tone and with downcast eyes, ‘that we need a man of remarkable strength. He must be able to spring from the floor to about twice his own height, gradually turning over as he rises, so as to come down again head first.’

      ‘Why, you need a flea, not a man!’ exclaimed the Sub-Warden.

      ‘Pardon me,’ said the Professor. ‘This particular kind of bath is not adapted for a flea. Let us suppose,’ he continued, folding his table-napkin into a graceful festoon, ‘that this represents what is perhaps the necessity of this Age—the Active Tourist’s Portable Bath. You may describe it briefly, if you like,’ looking at the Chancellor, ‘by the letters A.T.P.B.’