I can understand things less and less. Not that that matters, however. Whatever the colour of my guardians, the smallest movement of the sack must not let them suspect I've partly regained my freedom.

Slowly, carefully, I tug at my bonds, which gradually slide off my fists. Slowly, prudently, I succeed in moving my newly freed hands along my body.

That's what I've done. Now I've got to see.

I've got something that will help me. In my pocket is a knife . . . no, not a knife, a penknife. It's so small that it eluded my captors, but though I couldn't use it as a weapon, it's large enough to open a tiny window in this stifling sack. Now I've got to get hold of it without attracting attention.

After a quarter of an hour of patient effort, I succeed.

Thus armed, I bring my right hand up to the level of my face, and pierce the sack.

Heavens! . . . What can I see! ... I could only just keep back a cry of surprise. My eyes, facing towards the ground, see it at an enormous distance below, more than five hundred yards I should think. The truth flashes upon me. I am in a flying machine, which is carrying me through the air with the speed of an express train, or perhaps even faster.

Hardly are they open when my eyes close. A shudder runs through me from head to heels. Under the impact of that surprise, I don't mind admitting I'm scared.

When my heart regains its regular beat, I can observe more calmly. The ground is rushing dizzily below my eyes. What speed are we making? A hundred, two hundred, miles an hour? More? Whatever the answer, the soil is that of the desert, sand mixed with pebbles, with fairly numerous clumps of dwarf palm trees. A depressing country.

And yet I should have thought it would be worse. The dwarf palms are a bright green, and grass is growing abundantly between the pebbles. Contrary to general belief, does it rain sometimes in the desert?

Now and again I can make out, when they're below me, other contrivances like the one I'm in. My ears tells me that others are still higher. It is a flight of mechanical birds travelling through space. Serious though my position is, I get enthusiastic. It's a splendid sight, after all, and whoever our enemies may be, they are no ordinary people, those who have realized the ancient legend of Icarus in so masterly a fashion.

My field of view is not very great; so far as I can make out, thanks to slight movements which my guardians do not notice, I am looking between the plates of a metallic platform which restricts my view on eveiy side. Because of our height, however, the view is fairly wide.

But here the country's changing.