“Each of the four series of observations shows that the progress of the temperature is not regular at all heights, but that at a certain height (varying on different days) the regular diminution becomes arrested, and for the space of about 2,000 feet the temperature remains constant, or even increases by a small amount. It afterward resumes its downward course, continuing, for the most part, to diminish regularly throughout the remainder of the height observed. There is thus, in the curves representing the progression of temperature with height, an appearance of dislocation, always in the same direction, but varying in amount from 7° to 12°.
“In the first two series, viz.: August 17th and 26th, this peculiar interruption of the progress of temperature is strikingly coincident with a large and rapid fall in the temperature of the dew-point. The same is exhibited in a less marked manner on November 10th. On October 21st a dense cloud existed at a height of about 3,000 feet; the temperature decreased uniformly from the earth up to the lower surface of the cloud. When a slight rise commenced, the rise continuing through the cloud, and to about 600 feet above its upper surface, when the regular descending progression was resumed. At a short distance above the cloud, the dew-point fell considerably, but the rate of diminution of temperature does not appear to have been affected in this instance in the same manner as in the other series; the phenomenon so strikingly shown in the other three cases being perhaps modified by the existence of moisture in a condensed or vesicular form.
“It would appear, on the whole, that about the principal plane of condensation heat is developed in the atmosphere, which has the effect of raising the temperature of the higher air above what it would have been had the rate of decrease continued uniformly from the earth upward.”
These gentlemen do not adopt the absurd explanation of the French philosophers; they account for the phenomenon by supposing heat to be developed at that particular part of the atmosphere; but they are equally wide of the mark. They found the excess of heat there to the extent of 7° to 12°, and on days when there was no condensation, or other assignable cause for its development.
The temperature of the counter-trade partakes, doubtless, of the temperature of the adjoining strata at its upper and lower portion, and has never been found much, if any, higher than 60° at the center. Nor could it be expected. The trade, in its upward curving course, within the tropics, attains a considerable altitude where the atmosphere is comparatively cold, and necessarily loses a portion of its heat there, and during its northern flow. Probably its central summer range, in the latitude of Paris, is not far from 55°, and with us 60°.
The contrast between the trade and the surrounding atmosphere, in winter, is much more striking, and this has been observed particularly upon the Brocken of the Alps, and in the polar regions.
“In all seasons the temperature is higher on the Brocken, on a serene, than on a cloudy day, and, in the month of January, the serene days were warmer than at Berlin.” (Kämtz’s Meteorology, by Walker, p. 217.—Note.)
As the portion of the counter-trade, which does not become depolarized—in diminished volume—progresses toward the polar regions, it settles nearer the earth, and within the Arctic circle is found but little way above it. Thus, in December, 1821, Parry, at Winter Island, in latitude 66° 11′, flew a kite, with a thermometer attached, to the height of 379 feet, and found that the temperature, instead of falling 1¼°, the usual ratio of decrease, rose ¾ of a degree.
The same thing was observed at Spitzbergen, in latitude 77° 30′ north, and at Bosekop, latitude 69° 58′, by a scientific commission, and by means of kites, confined balloons, and the ascent of elevations.
“In winter the temperature goes on increasing with the height, up to a certain limit, which is variable, according to the different atmospheric circumstances, the influence of which is not yet very exactly known. The hour of the day appears to be indifferent, since there exists no thermometric diurnal variation in the strata of the surface. The mean of thirty-six experiments, made with kites, or with captive balloons, at Bosekop, latitude 69° 58′ north, has given a mean rate of increase of 1° 6′ for the first hundred meters.[6] Beyond this limit, and even beyond the first 60 or 80 meters, the temperature again becomes decreasing, at first very slowly, but afterward the decrease is accelerated. The observations that have been made on the flanks, or on the summits, of mountains, during the same expeditions, entirely confirm these results. The cooling influence of a soil, that radiates its own heat for several weeks, without receiving any thing on the part of the sun, in compensation of its losses, the influence of counter-currents from above, coming from the west and the south-west, with a high temperature, account for this anomaly, which, in winter, represents the normal state of the most northern parts of the European continent.” (Walker’s Kämtz, p. 515.—Note.)