These run in wet seasons, but in every instance for a short distance only, and sooner or later they are lost in sand-hills, where their waters disappear and a line of stunted gum-trees (Eucalyptus rostrata) is all that is present to indicate that there may be even a soakage to mark the abandoned course.
The honeycomb of rock, and capillary action, retard the lighter fresh-water from sinking to the sea; the soakage from rain has therefore to move horizontally, over the strata about sea-level, seeking outlets.
The bottom of the border as well as that Cymbidium Cypripedium Cyrtopodium Dendrobium Diacrium Disa Epidendrum Eulophia Eulophiella Galeandra Gongora Grammatophyllum Habenaria Houlletia lonopsis Ipsea Laelia Laelio-Cattleya* Leptotes Lissochilus Lycaste Masdevallia Miltonia Mormodes Odontoglossum Odontioda* Oncidium Peristeria Pescatorea Phaj us Phaio - calanthe* Phalaenopsis Pilumna Platyclinis Pleione Pleurothallis Polystachya Promenaea Renanthera Restrepia Rodriguezia S accolabium Schomburgkia Scuticaria Sobralia Sophro-cattleya* Sophronitis Spathoglottis Stanhopea Thunia Trichopilia Trichosma Vanda Zygo - colax* of the drain must be kept lower than the general level of the subsoil, else the soakage will gather in all the little depressions of its surface.
The desert was full of wild life, the balance of nature being preserved by the carnivorous animals preying on the herbivorous; trees watered by soakage from the Nile protected the undergrowth and encouraged occasional rainfall.