Le ciel est, par-dessus le toit, The sky is, up above the roof, Si bleu, si calme So blue, so calm Un arbre, par-dessus Je toit, A tree there, up above the roof, Berce sa palme. Waves leaves of palm. La cloche, dans le ciel qu'on voit, A church bell, in the sky I see, Doucement tinte. Softly tolls. Un oiseau, sur l'arbre qu'on voit, A bird, upon the tree I see, Chante sa plainte. Sadly calls. PAUL VERLAINE Like Verlaine, we are in prison. The prison is our Earth, "which is so pretty"; our atmosphere and its clouds, its "marvellous clouds." (You would think that Verlaine, Prevert and Baudelaire had been comparing notes ) The sky is up above the roof... A tree there, up above the roof... Stars in the sky, like birds ... their rays, like bells (and here we are with Apollinaire ) What we see opens the way to what we guess at; what we observe Ieads us towards the unobservable. A poem releases images, and the invisible grows big with reality. Astronomcrs are a little like poets (indirectly from the Greek 7tostco, make): they make the universe by interpreting messages, extrapolating spectra, and inventing 'models' of the cosmos or of stars - fictional constructions whose observable part constitutes only a small fraction of the whole, and which only the inductive logic of the theoretician allows us to consider as representing unique physical reality.

Among the many works devoted to our space environment, this serious and objective book by Mr. Delobeau should occupy a special place. It has become rare for works on such a subject to be written by competent physicists who are not specialists in the use of space vehicles. While performing research on the ionosphere, Mr. Delobeau was directly involved with the terrestrial environment long before it became common to explore it with sounding rockets and satellites. His professional obligations no longer require him to study aeronomy, only his regular collaboration with a great scientific journal inspires him to keep up to date on this subject. He is particularly motiva ted by a disinterested appreciation of the information which he hopes to share with his readers. It is a sign of the times that the results of space research should no longer be confined to the circle of space technicians. All of the new tools available to the service of science, for example:-particle accelerators, magnetic resonance, electron microscopy, lasers - have entered the general arsenal following a period of adaptation. Like them, the rocket is now a classical instrument, and gives information even to those for whom it holds no interest in itself. This book was quite up-to-date when the author submitted his manuscript. Despite the efforts of the editor, this will no longer be completely true when it appears in print. There is scarcely any branch of science that evolves more rapidly than space research.