Smoke Clouds. Use in an Invasion of Great Britain. Memo. Prepared under the Direction of the Director of the Meterological Office

against aerial observation will be reduced proportionately. It will be seen therefore, that although this effect tends to reduce the density of the smoke, it does not necessarily render the cloud ineffective even at great distances. IV. VERTICAL VISIBILITY IN THE SMOKE CLOUD. 9. During the first 10 miles of travel the height of the smoke cloud would not exceed about 2,000 feet, and the opacity of the smoke would be great. Such a cloud would undoubtedly be most effective against aerial observation.