“The steward ought to have something too,” said Mr. Twist.

“Oh, I’d be glad if you’d do him as well,” said Anna-Rose eagerly.  “I don’t think I could offer him a tip.  He has been so fatherly to us.  And imagine offering to tip one’s father.”

Mr. Twist laughed, and said she would get over this feeling in time.  He promised to do what was right, and to make it clear that the tips he bestowed were Twinkler tips; and presently he came back with messages of thanks from the tipped—­such polite ones from the stewardess that the twins were astonished—­and gave Anna-Rose a packet of very dirty-looking slices of green paper, which were dollar bills, he said, besides a variety of strange coins which he spread out on a ledge and explained to her.

“The exchange was favourable to you to-day,” said Mr. Twist, counting out the money.

“How nice of it,” said Anna-Rose politely.  “Did you keep your eye on its variations?” she added a little loudly, with a view to rousing respect in Anna-Felicitas who was lounging against a seat and showing a total absence of every kind of appropriate emotion.

“Certainly,” said Mr. Twist after a slight pause.  “I kept both my eyes on all of them.”

Mr. Twist had, it appeared, presented the steward and stewardess each with a dollar on behalf of the Misses Twinkler, but because the exchange was so favourable this had made no difference to the L5 notes.  Reducing each L5 note into German marks, which was the way the Twinklers, in spite of a year in England, still dealt in their heads with money before they could get a clear idea of it, there would have been two hundred marks; and as it took, roughly, four marks to make a dollar, the two hundred marks would have to be divided by four; which, leaving aside that extra complication of variations in the exchange, and regarding the exchange for a moment and for purposes of simplification as keeping quiet for a bit and resting, should produce, also roughly, said Anna-Rose a little out of breath as she got to the end of her calculation, fifty dollars.

“Correct,” said Mr. Twist, who had listened with respectful attention.  “Here they are.”

“I said roughly,” said Anna-Rose.  “It can’t be exactly fifty dollars.  The tips anyhow would alter that.”

“Yes, but you forget the exchange.”

Anna-Rose was silent.  She didn’t want to go into that before Anna-Felicitas.  Of the two, she was supposed to be the least bad at sums.  Their mother had put it that way, refusing to say, as Anna-Rose industriously tried to trap her into saying, that she was the better of the two.  But even so, the difference entitled her to authority on the subject with Anna-Felicitas, and by dint of doing all her calculations roughly, as she was careful to describe her method, she allowed room for withdrawal and escape where otherwise the inflexibility of figures might have caught her tight and held her down while Anna-Felicitas looked on and was unable to respect her.