LAMARCK'S WORK IN METEOROLOGY AND PHYSICAL SCIENCE When a medical student in Paris, Lamarck, from day to day watching the clouds from his attic windows, became much interested in meteorology, and, indeed, at first this subject had nearly as much attraction for him as botany.

For a long period he pursued these studies, and he was the first one to foretell the probabilities of the weather, thus anticipating by over half a century the modern idea of making the science of meteorology of practical use to mankind.
His article, "De l'influence de la lune sur l'atmosphere terrestre," appeared in the _Journal de Physique_ for 1798, and was translated in two English journals.

The titles of several other essays will be found in the Bibliography at the close of this volume.
From 1799 to 1810 he regularly published an annual meteorological report containing the statement of probabilities acquired by a long series of observations on the state of the weather and the variations of the atmosphere at different times of the year, giving indications of the periods when to expect pleasant weather, or rain, storms, tempests, frosts, thaws, etc.; finally the citations of these probabilities of times favorable to fetes, journeys, voyages, harvesting crops, and other enterprises dependent on good weather.
Lamarck thus explained the principles on which he based his probabilities: Two kinds of causes, he says, displace the fluids which compose the atmosphere, some being variable and irregular, others constant, whose action is subject to progressive and fixed laws.
Between the tropics constant causes exercise an action so considerable that the irregular effects of variable causes are there in some degree lost; hence result the prevailing winds which in these climates become established and change at determinate epochs.
Beyond the tropics, and especially toward the middle of the temperate zones, variable causes predominate.

We can, however, still discover there the effects of the action of constant causes, though much weakened; we can assign them the principal epochs, and in a great number of cases make this knowledge turn to our profit.

It is in the elevation and depression (_abaissement_) of the moon above and below the celestial equator that we should seek for the most constant of these causes.
With his usual facility in such matters, he was not long in advancing a theory, according to which the atmosphere is regarded as resembling the sea, having a surface, waves, and storms; it ought likewise to have a flux and reflux, for the moon ought to exercise the same influence upon it that it does on the ocean.