This is a difficulty with, for instance, Dodwell Rides Out (Radio 4, Sunday), in which over the last few weeks Christina Dodwell has been travelling around the remoter parts of Madagascar. This week, the last programme, she paddled up the Manambolo river to a rocky plateau where few have gone before, and was amazed by what she saw: "It's magic. All I can see in every direction is jagged stone pinnacles, picking up all the shadows and shapes in the light. Every side just a sea of impenetrability, canyons, grottoes, pinnacles, rocks, needles." A picture, you feel, would be worth a thousand words here - considerably more than a thousand unless the words got a lot more specific than this.
But then, this sort of travel programme doesn't find places interesting in themselves, they're only interesting because of the trouble the traveller goes through to get to them. Look at the title: no mention of Madagascar there, and indeed you find out surprisingly little about the island over 30 minutes (so that the claim in the closing credits, that "Christina Dodwell has been your guide to the island of Madagascar", rings rather hollow). But this is Dodwell's show, and it's her we're meant to wonder at - how intrepid she is, how determined, how indifferent to danger and discomfort. If you're amazed by the scenery, it's because you accept that if stoical old Dodwell is going to be amazed, it must be really amazing.
For all her hardy virtues, though, she is still basically one of us. Where Wilfred Thesiger, interviewed this week in The Art of Travel (Radio 4, Wednesday) was always keen to drop his English identity, blending in with his Arab friends, the imperturbable Englishness is an essential part of Dodwell's charm - the programmes are always charming, by the way. The fact that she speaks French with a heavily English accent makes her that much more out of place, that much more of an explorer; but it also makes her a far less glamorous, fascinating figure than Thesiger.
But Thesiger's big advantage over Dodwell is that he's talking in the past tense - in the case of his journey by camel across Arabia's Empty Quarter, 50 years past. It's not simply that he has had time to edit his story, to turn it into a series of neatly illustrative anecdotes, while Dodwell is rattling her thoughts straight into a tape recorder. The key moment in Thesiger's interview was when he assured Annette Kobak that he had had no thought of writing his experiences up until 10 years later, when a publisher persuaded him. That reluctance is a guarantee of authenticity: you know that he made the journey for its own sake, not because he thought it would make good material. The very fact that she has a tape recorder deprives Dodwell of a sort of purity - it's like the difference between putting away a criminal through good police work and doing it by entrapment.
If you want to take that analogy a bit further, though, Dodwell is essentially the bobby on the beat, while the five students in this week's Tales from the Back of Beyond (Radio 4, Tuesday) came across more as a kind of Riot Squad - confronting the public from behind batons, shields and plastic visors.
They were on an expedition to north India to find out how well an exiled Tibetan community was preserving its distinctive culture. You didn't hear much about the Tibetans - though it may be that they recorded a lot of material on this topic which later hit the cutting-room floor - but it's a pretty safe bet that they were doing better than the students, who became increasingly paranoid and irritable as the weeks wore on.
The programme ended with some optimistic words about the future of the Tibetan exiles; but that was just a post-script. The real message was this: travel may well broaden the mind; but sometimes, it narrows it.