Type 6 shows a less common, but an interesting form, of vertical distribution of temperature, in which the temperature is about the same from 400 metres to 1400 metres or more. Up to 400 metres there is a fall of temperature with increasing altitude during the day, and a rise with increasing altitude at night. These last conditions can be readily traced to the effects of insolation and radiation near the ground. In the morning, if the temperature of the air be the same from the ground up to 1000 metres or more, the heating of the ground by the sun will cause ascending currents, until the warmest part of the day. This air, cooling by expansion at the adiabatic rate, will rise to about 440 metres before it assumes the mean temperature of the upper air column. At night cooling takes place next the ground by radiation and is gradually transferred upward a few hundred metres by conduction, thus producing an increasing temperature with increasing altitude, until sunrise. As a result of the conditions described, it is evident that on certain days the diurnal range of temperature is but little felt above 500 metres. =Types of Change of Relative Humidity with Altitude.=--As in the temperature types, the continuous lines represent the records of the ascent, and the broken lines the records of the descent, generally under changing conditions. Lines inclining upward to the left show a decreasing humidity, and to the right an increasing humidity. Type 1 may be called a normal type of curve when there are clouds. A variation of this type was met with in the ascent on October 8, 1896, and it differed from that now illustrated in indicating in its upper part a fall of humidity rather than a rise. These two types can be taken as the normal change of humidity with change of altitude in cloudy or partly cloudy weather. The humidity increases steadily to the base of the cloud, then there is complete saturation in the cloud, and above it is a sudden fall of humidity, on entering the dry air above the cloud, into which the ascending currents from the ground have not penetrated. Type 3 is a clear-weather form of curve in which the humidity increases until a certain altitude is reached, probably at the upper limits of the currents rising from the ground. Above this altitude the humidity decreases rapidly. Type 5 is also a clear-weather form and accompanies the "cold wave" type of temperature, also numbered 5. The very dry descending air mingles with air rendered damp by ascent, and the result is a nearly uniform relative humidity at different altitudes, although the absolute humidity diminishes on account of decreasing pressure and temperature. In Type 6 both the relative and the absolute humidity decrease rapidly, this type coinciding with the temperature, Type 6.