(2) Collecting and evaporating all tank waters. (3) Drying of tankage done under vacuum or otherwise controlling odors. (4) Catch basins under cover, skimmed frequently and contents cooked promptly. (5) The rendering department kept tightly closed and department operated with forced draft, all discharged air passed through large water-wash, and the introduction into the air of gas boiled from tar oil. (6) All tank exhaust and vapors connected to a piping system, the steam condensed by water spray, and the vapor collected and passed under furnaces of boilers. (7) Keep everything hot, allow nothing to lay around and sour. =Catch Basin.=--Every packing house needs an adequate catch basin system. Local basins established in departments near to points where products are handled, serve to collect many fats and oils that, by clean handling, are edible products, and can be used as such. Where melted fats are produced cold water sprays should be introduced to coagulate the oils. Wiers for over and under-flow should be put in to retard flow and submerge particles so they may harden and float. A large general basin should be introduced so that all outflowing sewers can be passed to them, to the end that all water flows slowly through the basin to catch any and all particles of floating fats or meats. The basins should be placed under the care and jurisdiction of one person, who should see that they are kept clean and frequently skimmed. It is to good purpose to place them under roof so they will have attention at all times. CHAPTER XV. TANK WATER. SOIL FERTILITY -- ANIMAL FEEDING -- TANK WATER -- SEPARATION OF SOLIDS -- COLLECTING GREASE -- TESTING TANK WATER -- EVAPORATING TANK WATER -- DESCRIPTION OF APPARATUS -- CLEANING EVAPORATORS -- TABLE OF BOILING POINTS -- TESTING STICK -- COPPERAS IN WATER TO EVAPORATE -- SOLIDS IN WATER -- DRYING STICK -- VALUE OF TANKAGE -- QUANTITY OF TANK WATER -- COST OF EVAPORATING. =Soil Fertility.=--The constant drain on the soil by raising of grain; feeding animals and sending them away for slaughter, and the non-return of the nitrogen element has made great inroads on the productivity of soil. Through volume after volume and in every manner possible, economic writers are impressing this upon the agricultural interests and advocating the making up of such deficit by rotating crops, turning under legume and plants that might extract nitrogen from the air by the processes of nature which daily are becoming more familiar to every one. Value and demand for the nitrogenous elements for this purpose has caused the packer to exercise all possible care to produce and conserve for sale any and all nitrogenous products.