[12th October 1916] sand, the other of the wastes of snow. Meteorologists maintain that three conditions are essential for the production of a true blizzard*. (1) A wind of extremely high velocity; (2) Intense cold; (3) an atmosphere laden with driving snow. In the East these conditions are attained in the higher altitudes of the Himalaya and in the wind-swept plateaux of Thibet and the Pamir. It is probable that in the British Isles they can never occur so that the blizzard, like the dust-storm, must remain unknown in those islands.
But Asia is the true home of the dust-storm; it rages with great intensity over the vast deserts of the continent. And as in the blizzard, so also in the dust-storm, three physical essentials are necessary for its production. Firstly, in resemblance to the blizzard, there must
*Correspondence in Nature of 22.6.16 & previous issues