Inversions of Temperature. Possibilities for Large Scale Use of Gas or Smoke over the United Kingdom. Note by the Secy.

(1) ADVANTAGES. (i) The release of 3,700 tons per hour of D.C. smoke is within the capabilities of the German Chemical Industry. (ii) Although the suitable occasions for this operation are only 9 per annum, these periods are of reasonable duration. (iii) A further point of importance is that by the time the cloud reached England, it would be almost invisible and sufficiently attenuated to be casualty-producing before its presence was realised. (iv) While inversions are more likely to occur over the continent than over England in Winter, yet such inversions cannot be used by us in the same way as by the enemy, and are only widespread when the wind is from some Easterly point.