100 YEARS AGO All persons who interest themselves in the progress of celestial mechanics, but can only follow it in a general way, must feel surprised at the number of times demonstrations of the stability of the solar system have been made. Lagrange was the first to establish it, Poisson then gave a new proof; afterwards other demonstrations came, and others will still come. Were the old demonstrations insufficient, or are the new ones unnecessary? The astonishment of these persons would doubtless be increased if they were told that perhaps some day a mathematician would show by rigorous reasoning that the planetary system is unstable. ⃛ It can be shown, in certain particular cases, that the elements of the orbit of one planet will return an infinite number of times to very nearly the initial elements, and that is also probably true in the general case; but it does not suffice. It should be shown that these elements will not only regain their original values, but that they will never deviate much from them. This last demonstration has never been given in a definite manner, and it is even probable that the proposition is not strictly true. — M. H. Poincaré.
From Nature 23 June 1898.
50 YEARS AGO The French Association of Scientific Workers is organising an International Holiday Centre at Morzine (Haute-Savoie) during July 15-September 1. Morzine, without being a fashionable holiday resort, is one of the beauty spots of the French Alps. It lies to the south of Thonon at a height of about 1,000 metres; and around it are ranges rising to about 2,500 metres. So far as hotels are concerned, the French Association of Scientific Workers can secure accommodation at 800 and 700 francs a day (including service and taxes). It has also secured some good camping sites, and is trying to make arrangements for a canteen. Bookings can only be made for whole weeks (from Monday morning to Sunday night) and for a minimum of two weeks; registration fee, 500 francs each person. Applications should be made as soon as possible to the Association des Travailleurs Scientifiques, Maison de l'Université Française, 47 Boulevard St. Michel, Paris 5.
From Nature 26 June 1948.