THE National Smoke Abatement Society has issued its quarterly, Smokeless Air,on a reduced scale but with a supplement “Smoke Abatement in War Time”. This is an effort to rebut the belief that reduction of smoke under present conditions is unimportant. The impression that smoke serves a useful purpose by screening towns against air attack is challenged. A smoke screen may assist a moving object such as a ship, but serves as a landmark fixing the position of a stationary group such as a town. It may provide a screen to hinder the recognition of a specific object, but equally it conceals the attacker from the defence. Concealment is a great help to the submarine, and recent experience shows its assistance to raiding aircraft. The pamphlet directs attention to the way in which colliery tips serve as landmarks, providing a “difficult problem” in smoke abatement. The difficulty, it may be indicated, is less technical than political and due to the fact that the disposal of pit refuse is left to the discretion of the individual colliery. Naturally the cheapest possible method is used, regardless of the effect on the surrounding people, land and of the ultimate cost to the community. The chemical composition of pit refuse is such that self-ignition can scarcely be prevented when it is dumped in enormous heaps. Too often collieries are surrounded by low-lying land reduced to valueless swamp by mining subsidence. Pit refuse would serve a useful purpose, if used to raise the level of such land, and under such conditions firing would not occur.