A towel, it says, is about the most massively useful thing an interstellar hitchhiker can have. Partly it has great practical value - you can wrap it around you for warmth as you bound across the cold moons of Jaglan Beta; you can lie on it on the brilliant marble-sanded beaches of Santraginus V, inhaling the heady sea vapours; you can sleep under it beneath the stars which shine so redly on the desert world of Kakrafoon; use it to sail a mini raft down the slow heavy river Moth; wet it for use in hand-to- hand-combat; wrap it round your head to ward off noxious fumes or to avoid the gaze of the Ravenous Bugblatter Beast of Traal (a mindboggingly stupid animal, it assumes that if you can't see it, it can't see you - daft as a bush, but very ravenous); you can wave your towel in emergencies as a distress signal, and of course dry yourself off with it if it still seems to be clean enough.

More importantly, a towel has immense psychological value. For some reason, if a strag (strag: non-hitchhiker) discovers that a hitchhiker has his towel with him, he will automatically assume that he is also in possession of a toothbrush, face flannel, soap, tin of biscuits, flask, compass, map, ball of string, gnat spray, wet weather gear, space suit etc., etc. Furthermore, the strag will then happily lend the hitchhiker any of these or a dozen other items that the hitchhiker might accidentally have "lost". What the strag will think is that any man who can hitch the length and breadth of the galaxy, rough it, slum it, struggle against terrible odds, win through, and still knows where his towel is is clearly a man to be reckoned with.

Hence a phrase which has passed into hitchhiking slang, as in "Hey, you sass that hoopy Ford Prefect? There's a frood who really knows where his towel is." (Sass: know, be aware of, meet, have sex with; hoopy: really together guy; frood: really amazingly together guy.)

• Take the juice from one bottle of that Ol' Janx Spirit, it says.


• Pour into it one measure of water from the seas of Santraginus V - Oh, that Santraginean sea water, it says. Oh those Santraginean fish!!!


• Allow three cubes of Arcturan Mega-gin to melt into the mixture (it must be properly iced or the benzene is lost).


• Allow four litres of Fallian marsh gas to bubble through it (in memory of all those happy Hikers who have died of pleasure in the Marshes of Fallia).


• Over the back of a silver spoon float a measure of Qualactin Hypermint extract, redolent of all the heady odours of the dark Qualactin Zones; subtle, sweet, and mystic.


• Drop in the tooth of an Algolian Suntiger. Watch it dissolve, spreading the fires of the Algolian suns deep into the heart of the drink.
  
• Sprinkle Zamphour.


• Add an olive.


• Drink... but... very carefully...

For instance, on the planet Earth, man had always assumed that he was more intelligent than dolphins because he had achieved so much - the wheel, New York, wars and so on - whilst all the dolphins had ever done was muck about in the water having a good time. But conversely, the dolphins had always believed that they were far more intelligent than man - for precisely the same reasons.

Curiously enough, the dolphins had long known of the impending destruction of the planet Earth and had made many attempts to alert mankind of the danger; but most of their communications were misinterpreted as amusing attempts to punch footballs or whistle for tidbits, so they eventually gave up and left the Earth by their own means shortly before the Vogons arrived.

...in fact the message was this: So long, and thanks for all the fish.