Page:Popular Science Monthly Volume 18.djvu/727

Rh off a little of the liquid, when, if it is of a pale straw-color, the quantity of indigo will not be so great, but the quality will be better than when it is of a deep-yellow tinge. The liquid, when it is drawn off after fermentation, is always of a more or less deep-yellow color. It is allowed to remain for some little time, and is then, while still warm, beaten with long bamboos for two or three hours. It gradually becomes of a pale green color, and the indigo forms into small flakes. The mass is allowed to remain for half an hour, and the water is then turned off gradually by withdrawing one by one corks which have been placed at different levels in the vat. The water is returned to the river, and the deposit, which resembles a thin scum, is carried through a trough into a deep trench. It is then brought up and boiled for a short time to prevent a second fermentation, which would turn it black and spoil it. After about twenty hours, it is again boiled for three or four hours; then poured off, and strained through a filter. A thick, deep-blue paste, almost black, remains on the cloth of the filter after the liquid has been strained through. This paste is exposed to a pressure, which removes every particle of moisture, after which the indigo is found in a large, thick block, the cutting of which demands extreme care. The blocks are put in the drying-ground, a large brick building from which the light of the sun is carefully excluded, and, after from three to four days, are ready to be sent to the market.

Purification of River-Water by Organic Agents.—Mr. R. Warrington, in "The Chemical News," notices that, in the discussions on the qualities of river-water, the destruction of sewage which takes place in such water is in every case referred to the oxidizing influence of the air, and the action of organic agents is overlooked. Yet it is evident, and generally admitted, that these agents play an important part in the change of organic into inorganic matter. The process is in effect the joint work of a number of independent organisms having different functions, the action of one class following that of another, and each carrying the process through a particular stage. First are the fungi, whose main function is apparently the rapid oxidation of carbon; then come the bacteria, embracing many families of similar physical structure, but endowed with very different chemical powers. One class attacks nitrogenous organic matter and liberates nitrogen in the form of ammonia; another determines the conversion of carbonaceous organic matter into inorganic carbonic and nitric acids. Lastly come the chlorophyl-bearing plants to consume these products of the lower organisms; they also have the property of assimilating urea and inorganic ash constituents. These organisms must follow in their order, or they will fail to do their work. Sewage will finally be destroyed in a river of adequate temperature, unless the natural agents of oxidation are excluded by the addition to the water of chemical refuse fatal to organic life, or unless vegetation is prevented by artificial means. Temperature and light, or rather darkness, are important factors in the process. The experiments show that the oxidation in rivers increases as the temperature rises. The amount of dissolved matter in rivers is found to be greatest in February, when organic action is suspended, and least in September and August, when the action is most energetic.

Mind in Work.—It is set forth on the highest authority that whatever we do should be done with our might. This precept being interpreted means that there should be mind in work. The difference between a work of art and the product of machinery lies in the presence of a mark of mind directing the handiwork in the one case, while the other is simply a predetermined result produced by a duly formulated process wherein or whereby physical forces are directed and controlled by other physical forces on a sot plan, to perform a defined series of actions, which must, in the nature of things, end in the production of the effect foreseen. Mind sets the one process, or series of processes, in operation, and they work out their physical destinies. In the other, mind is the active controlling power throughout. Starting from these premises, we are now concerned to point out that little or no success can be expected in any calling which does not suit the temper and bias of the mind