In 1815 Goethe becomes acquainted with Luke Howard's Attempt at a Natural History and Physics of the Clouds. He is stimulated by it to sharpen his reflection about cloud formations and atmospheric conditions. He had in fact already made many earlier observations about these phenomena and recorded them. But he lacked “overview and branches of science to connect with” in order to bring together what he had experienced. In Howard's essay the manifold cloud formations are traced back to certain basic forms. Goethe now finds entry into meteorology, which until then had remained foreign to him because for his nature it was impossible to gain anything from the way this branch of science was handled in his time. “For my nature it was impossible to grasp the whole complex of meteorology in the way it was set up in tables of numbers and symbols; I was glad to find an integrating pan of this science to be in accord with my inclination and life, and, because everything in this endless universe stands in eternal sure relationship, because one thing brings forth the other or is brought forth by it, I sharpened my gaze for what the eyes can grasp and accustomed myself to bring the interconnections of atmospheric and earth phenomena into harmony with the barometer and thermometer ...”
Since the level of barometric pressure stands in an exact relationship to all weather conditions, it soon came for Goethe into the center of his observations of atmospheric conditions. The longer he continues these observations the more he believes he recognizes that the rise and fall of mercury in the barometer at different “places of observation, whether they be nearer or farther away or of varying length, breadth, and height,” occurs in such a way that for a rise or fall in one place there corresponds an almost equally great rise or fall at all other places at the same time. From this regularity of barometric changes Goethe draws the conclusion that no influences outside the earth can affect these changes. When one ascribes such an influence to the moon, planets, seasons, when one speaks of ebb and flow in the atmosphere, then the regularity is not explained. All these influences would have to manifest themselves at the same time in different places in the most different ways. Only when the cause of these changes lies within the earth itself are they explainable, Goethe believes. Since the level of mercury depends upon atmospheric pressure, Goethe pictures to himself that the earth alternately compresses the whole atmosphere and expands it again. If the air is compressed then its pressure increases and the mercury rises; the opposite occurs with expansion. Goethe ascribes this alternating compression and expansion of the entire mass of air to a changeability to which the earth's force of gravity is subjected. He sees the increase and decrease of this force to be founded in a certain individual life of the earth, and he compares it to the inbreathing and outbreathing of an organism.
In accordance with this Goethe also does not think of the earth as active in a merely mechanical way. Just as little as he explains geological processes in a purely mechanical and physical sense does he do so in regard to barometric changes. His view of nature stands in sharp opposition to the modern one. The latter seeks, in accordance with its general basic principles, to grasp atmospheric processes in a physical sense. Differences of temperature in the atmosphere bring about a difference of atmospheric pressure in different places, create air currents from warmer to colder regions, increase or decrease humidity, bring forth cloud formations and precipitation. Out of these and similar factors the variations in atmospheric pressure, and with them the rise and fall of the barometer, are explained. Goethe's picture of an increase and decrease in the force of gravity is also in opposition to modern mechanical concepts. According to them the strength of the force of gravity at any one place is always the same.
Goethe applies mechanical conceptions only to the extent that observation seems to dictate.