Page:The aquarium - an unveiling of the wonders of the deep sea.djvu/330

Rh reservoir, at some distance above the level of the Tank, in a higher story for example, whence a supplying tube may descend, and passing beneath the floor, ascend through the foot of the vase, to the surface of the water. All the visible portion may be easily concealed among the rock-work; while from the extremity a jet would play, proportioned in force to the weight of the supplying column, or, in other words, to the height of the reservoir above the surface. It would be needful to make the apparatus of some incorrodible material;—gutta percha, for instance, for the tube, with a nozzle of glass;—as metals would be acted on by the sea-water, and form noxious oxides. The water might either be carried up to the reservoir, or pumped up by an obvious extension of the apparatus.

Such a modification would doubtless be as efficient as it would be elegant. The constant, or at least, frequent dissemination of the water through the air would keep the whole volume in agreeable coolness, as well as maintain its sparkling clearness and purity.

Evaporation.—If the Tank remain habitually uncovered, or protected only by a coverlid of muslin, daily evaporation will soon reduce the volume of the water, and increase its specific gravity. The pure water alone rises in vapour, the various salts held in solution, remaining the same in quantity, though the water should be reduced to half its original bulk. It is therefore needful that additions of pure fresh water (not sea-water) be made from time to time, to replace the loss by evaporation. Distilled water is of course the best, but, practically, river-water will answer