'I compare the earth and her hygrosphere3 to a great living being perpetually inhaling and exhaling. If she inhales, she draws the hygrosphere to her, so that, coming near her surface, it is condensed to clouds and rain. This state I call water-affirmative (WasserBejahung). Should it continue for an indefinite period, the earth would be drowned. This the earth does not allow, but exhales again, and sends the watery vapours upwards, when they are dissipated through the whole space of the higher atmosphere. These become so rarefied that not only does the sun penetrate them with its brilliancy, but the eternal darkness of infinite space is seen through them as a fresh blue. This state of the atmosphere I call water-negative (WasserVerneinung). For just as, under the contrary influence, not only does water come profusely from above, but also the moisture of the earth cannot be dried and dissipated - so, on the contrary, in this state not only does no moisture come from above, but the damp of the earth itself flies upwards; so that, if this should continue for an indefinite period, the earth, even if the sun did not shine, would be in danger of drying up.' (llth April 1827.) Goethe's notes of the results of his meteorological observations show how in them, too, he followed his principle of keeping strictly to the phenomenon. His first concern is to bring the recorded measurements of weather phenomena into their proper order of significance. To this end he compares measurements of atmospheric temperature and local density with barometric measurements. He finds that the first two, being of a more local and accidental nature, have the value of 'derived' phenomena, whereas the variations in the atmosphere revealed by the barometer are the same over wide areas and therefore point to fundamental changes in the general conditions of the earth. Measurements made regularly over long periods of time finally lead him to recognize in the barometric variations of atmospheric pressure the basic meteorological phenomenon.