Since there appears to be no appreciable diurnal period in the temperature at and above 500 metres, a better comparison of the relative changes aloft and below during the passage of warm and cold waves is obtained by smoothing out the diurnal period below. This has been done in Plate XI., Fig. 4, with the data given by the kites at 500 and 1000 metres plotted in curves, which it was necessary to complete by extrapolation. It is seen that there is a much greater range in the temperature from the crest of a warm to the crest of a cold wave at a height of 500 metres than at the ground. At 1000 metres the range appears to be slightly greater than at 500 metres, and the crests of the warm and cold waves occur successively earlier than they do at the ground. On the approach, and until the passage of the crest of the cold wave the air is colder aloft than at the ground, the difference being apparently that of the adiabatic cooling of ascending air. After the passage of the crest of the cold wave, the temperature aloft rises much more rapidly than at the ground, and at the crest of the warm wave the air at 500 metres is some 10° warmer than the mean daily temperature at the ground. In many kite-flights the difference was found to be even greater than this. Taking the mean temperature of twenty-four hours, it is seen that the average temperature at the ground during a week or more is about the same as it is at 500 metres. Fig. 5 shows the change in the vertical distribution of temperature during the oncoming of the warm wave on the eighth and early morning of the ninth, as determined by four ascents, culminating at 11 a.m., 9 p.m., II p.m., and 4 a.m. The lines of 59°, 62°, 65°, and 68° show that there was a gradual rise of temperature aloft, which extended downwards to 200 metres, or to the top of Blue Hill. Clouds formed at the level of lowest temperature, and these sank also until they covered the top of the hill. Plate XII. is a facsimile of the meteorogram during the kite-flight of October 15, 1897, the lower part showing the trace of the barometer on a scale of heights in metres, the middle section the trace of the hygrometer, and the upper one the trace of the thermometer on a scale of Centigrade degrees. The temperature followed the normal change, which is as follows: during the day, up to a certain height, which varies under different conditions, there is a decrease nearly at the adiabatic rate of 1°8 F. per hundred metres. Above that height the air suddenly becomes warmer, and then cools with ascent at a rate somewhat less than the adiabatic rate. During the night there is a marked inversion of temperature between the ground and 200 or 300 metres. Higher than this, the temperature decreases at a fairly uniform rate, but more slowly than the adiabatic rate. Although no clouds were visible, yet the relative humidity increased greatly, both during the ascent and descent, near 1500 and 2700 metres, these being about the heights at which cumulus and alto-cumulus clouds usually form. During September 1898 four kite-flights were made on four successive days when an anti-cyclone and a cyclone passed nearly over Blue Hill. This is a rare occurrence, and the mechanism of these phenomena was accordingly studied by Mr. Clayton, some of whose deductions will now be given, illustrated by Plate XIII. Figs. 1 and 2 give the temperature plotted according to height on September 21 in the anti-cyclone, and on September 22, when the barometric pressure was falling, the full lines, as in previous diagrams, indicating observations during the ascents, and the broken lines observations during the descents. It is seen that from the ground the lines all incline upward to the left, indicating a fall of temperature, to a certain height when the lines bend to the right sharply, showing a sudden rise of temperature. Above this, the temperature again falls, but more slowly than at lower levels. The general prevalence of this phenomenon was noted by Welsh in his balloon ascents in England in 1854, and the high |