Effective incendiary bombing calls for random distribution of 14in, 2-lb. bombs. In a city like London, in which the ratio of buildings to open space is one to four. not more than 20 per cent. of the bombs, dropped ten or twenty at a time in "Molotov breadbaskets," can be expected to take effect. Chance duds and well-organized defence reduce the percentage further, so that not more than one in twenty bombs is likely to start a really troublesome fire.
Most spectacular British contribution to incendiary warfare were the "calling cards" dropped by British bombers over German farm lands last autumn These were discs of absorbent paper, impregnated with a solution of phosphorus and dampened with water. Harmless as long as it is kept moist, the phos-chorus bursts into flame as soon as the water has evaporated. Scattered far and wide in the open country, "calling cards" offer a potent and hard-to-control weapon against the enemy's crop and forest resources. Printed with intrigue ing messages, they may burn curious citizens and even be carried innocently into houses, setting them afire.
An important element in incendiary bombing is variation of materials for purpose of confusing defenders. As demonstrated by Germans in attacks on London, this calls for the occasional use of less effective. oil bombs, which require different extinguishing techniques. Blunt-nosed incendiary bombs, dropped from altitudes above 5,000 ft, strike at speeds of about 380 ft. per sec. They do not usually penetrate below attic floors and thus start most of their fires on roofs or in upper stories. Still to be exploited is a wide variety of incendiary chemicals which may come into use with in. creased demand for aluminium and magnesium in their more constructive functions.
Text read from the printed page and cleaned; old type leaves the occasional error.