In the year 1815, Goethe became acquainted with Luke Howard's Essay on the Natural History and Physics of Clouds. This stimulated him to more penetrating thought concerning cloud formations and meteorological conditions. He had, indeed, already made and noted down many observations concerning these phenomena. He had, however, neither a general view nor an acquaintance with related branches of science which could have enabled him to correlate what he had observed. In Howard's Essay, the manifold cloud formations are traced back to certain basic forms. Goethe now finds an entry into meteorology, a science which had previously remained foreign to him because he could learn nothing from the way in which it was handled in his time. “It was impossible for my nature to comprehend the whole complex of meteorology, arranged as it is in a series of tabular signs and numbers; I was glad to find an integral part of it responding to my inclination and mode of life, and because in this infinite All everything stands in eternal, secure relation, one thing bringing forth or reciprocally brought forth by the other, I concentrated my attention on what the eyes can ‘lay hold of,’ and accustomed myself to bring the relations of atmospheric and earthly phenomena into harmony with the barometer and thermometer.”
Since the barometric height stands in an exact relation to all meteorological conditions, it soon became, for Goethe, the central point of his observations on atmospheric conditions. The longer he continued these observations the more was he convinced that he found the rise and fall of the mercury in the barometer at different “places of observation, nearer or farther away, at different longitudes, latitudes and heights,” occurring in such a way that the rise or fall at one place corresponded to an almost equal rise or fall at all other places at the same time. From this regularity in barometric changes Goethe draws the conclusion that no influences outside the earth are able to affect them. Where such an influence is ascribed to the moon, the planets, or the seasons, and one speaks of an ebb and flow in the atmosphere, this regularity is not explained. All these influences would have to make themselves felt at the same times in the most diverse ways at different places. Goethe is of opinion that these changes are only explicable if the cause of them lies in the earth itself. Since, however, the height of mercury depends on the pressure of the air, Goethe imagines that the earth alternately presses and again expands the whole atmosphere. If the air is compressed its pressure increases and the mercury rises; the reverse takes place with expansion. Goethe ascribes this alternating contraction and expansion of the whole mass of air to a variation to which the attractive power of the earth is subject. He regards the increase and decrease of this force as inherent in a certain individual life of the earth, and compares it with the inbreathing and outbreathing of an organism.
Accordingly Goethe does not conceive of the earth as being active in a merely mechanical sense. Just as little as he explains geological processes in a purely mechanical and physical sense does he do so in regard to barometric variations. His view of Nature stands in sharp contrast to that of modern times which seeks, in accordance with its general basic principles, to understand atmospheric processes physically. Differences of temperature in the atmosphere bring about a difference of air-pressure in different places, give rise to air-currents proceeding from warmer towards colder regions, increase or diminish the amount of moisture and give rise to cloud formations and condensation. The variations in air-pressure, and therewith the rise and fall of the barometer, are explained by such factors or by others similar to them. Goethe's conception of an increase and decrease in the force of attraction is also contrary to the concepts of modern mechanics. According to these the strength of this attractive force is always the same in one place.
Goethe applies mechanical conceptions only to the extent to which observation appears to him to demand.