Note 53 — APPENDIX A. ON THE FALL OF TEMPERATURE IN ASCENDING TO HEIGHTS ABOVE THE SEA-LEVEL.
Reading edition
Air nearly saturated with vapour is lighter than air relatively dry; and hence it may happen that, when a current of moist air meets one relatively dry, it will flow over the latter if they are nearly at the same temperature, but if the drier current be much warmer, it may flow beneath it.