The strong development of industry, the increase in population, and the ever-increasing prosperity have all created new problems: our environment has become damaged to a dangerous degree by fluid, solid and gaseous pollutions from industry, trade and household. The cleansing of our waters may be said tobe satisfactory in Switzerland. By the middle of the present decade about 60% of the population and a great part of the industry will be provided with water cleansing works andrefuse disposal centres. But with the building of these works alone, the problem is not solved. Numerous unsolved problems and expensive measures are still before us if we wish to protect our atmosphere, waters and soils from destruction. For example, the question of the removal of the scum from the sewage works is not yet satisfactorily solved in many parts of Switzerland. Not only a surplus of scum but also serious anxiety on the part of the veterinary experts makes the practice of using the scum in the simplest and most economic way as agricultural manure, ever more problematic. Furthermore, the removal of much of the refuse from industry and commerce nowadays causes great difficulties. The pollution of the atmosphere by gases from house chimneys, from automobile exhausts and from industrial manufactories appears to be less serious in Switzerland, according to the experts, than in rnany other countries. However, we need to rnake every effort to rnaster for the future this undoubtedly threatening danger. The duty to keep our environrnent clean involves not only the protection of water and air, but also the protection of the land. Water, land and air form our natural environrnent: a unity which we have to protect frorn deteriora tion.