“What is the cause of such reflection?” La Cueille asked. “I’m just considering,” Wienersdorf answered, “and will try and explain my opinion respecting its formation. The enormous evaporation to which the mass of water is exposed, on a marshy soil like Borneo and under the influence of a tropical sun, causes more clouds to be formed here than anywhere else on the globe. I imagine that with a very dry and perfectly calm atmosphere these vapors formed above each sheet of water rise perpendicularly, and arrived in higher regions, concentrate into these feathery clouds now seen by us up there. If it is equally calm in those upper regions these clouds will concentrate above the waters from which they have originated and present their exact counterpart.” “Beautifully explained,” Schlickeisen remarked, “but one more explanation before I propose a vote of thanks to our comrade. You said that feathery clouds rise after evaporation formed from every sheet of water. Now, as the whole of that part of marshy Borneo in which we now are may be considered as forming a coherent sheet of water, if the formation takes place in the manner described by you, how is it that only the image of one river or stream is given? And why is not the whole firmament covered with a similar network of clouds?” “So it would be,” Wienersdorf replied, “if the evaporation could take place undisturbed above these marshy grounds; or in other words, if what takes place above rivers and lakes could occur everywhere. But the dense foliage of the virgin forest is spread out over these marshes and forms as it were a roof difficult to penetrate. At night radiation takes place, the branches and leaves cool down and the rising mist condenses against them in the same manner as the particles of moisture are deposited against the window of a heated room. See for yourself whether the trees are covered with an abundant dew or not. This dew would have formed the feathery clouds if only allowed to rise. It will evaporate fast enough as soon as the branches and leaves have acquired the same temperature as the surrounding atmosphere. The forest, therefore, in regard to the evaporation, forms a horizontal roof, a plain which is only intersected above the rivers, soengeis, lakes, etc., and allows the evaporated atoms of water to escape during the first hours of the morning. Elsewhere those atoms are held bound down. I trust I have given you a satisfactory explanation. To myself these reasons suffice to explain the origin of the magnificent air-picture which we just now admired, but which has disappeared, dispelled by the south-eastern wind.” “I am perfectly satisfied and delighted with your mode of explanation,” Schlickeisen replied.