So Bob looked at his watch, and it was exactly six p.m!

Being a member of the Lewis Carroll Society, Bob knew what Lewis Carroll would have said about relying on a stopped clock.

"If you have the choice of two clocks, one which has stopped and one which loses a minute a day, which do you choose?"

"The losing one," you answer, "without a doubt."

"But," says Carroll, "The one which loses a minute a day has to lose seven hundred and twenty minutes before it is right again, so it's only right once in two years. But the other is right as often as the time it points to comes round - which happens twice a day."

So the stopped clock is evidently the best!

But, you might go on to ask, "How am I to know when six o'clock does come? My clock will not tell me."

To which Carroll replies, "Be patient: you know that when six o'clock comes your clock is right.. Keep your eye fixed on your clock, and the very moment it is right it will be six o'clock."

"But--," you say.

"There, that'll do; the more you argue the further you get from the point."

So just to be on the safe side, Bob had a working watch too. But when he checked it, he found that the stopped clock WAS exactly right. Six o'clock, and time for this evening's Lewis Carroll Society meeting. And very interesting it was too, in a most unusual building which I will tell you about next time.