SIBIOOM (Ar. sanriim, hot pestilent wind, from summa, to poison). A hot suffocating wind, carrying clouds of dust. Although these winds occur in their greatest intensity in the deserts of Northern Africa and Western Asia, analogous w•imls are found in India, North America, and Aus tralia. Simooms may be either local and similar to our hot winds, sand storms, and tornadoes, or they may he more general, like the blizzards of North America or the bora of Northern Europe. Owing to the clear sky over desert regions in the tropics, the soil and adjacent air may become intensely heated, causing local ascending currents and whirlwinds. Temperatures of 120° and 140° F. have been observed in the Sahara and are not infrequent in Arizona, New Mexico, and Australia. The descriptions of the simoom indicate that as it approaches the ob server its front extends at least from five to twenty miles, very much like the ad vancing front of a series of thunder storms on a hot afternoon; the clouds of line sand and dust that are carried up by the wind extend as a haze overspreading the sky: the heavier sands are also transported in large quantities, and as they fall are collected in mounds around every obstacle like the drifts of snow in winter. In the case of an extended simoom the finer sands are carried so high as to be drawn into the general circulation over Europe. Thus in the great storm
of March 10-12 1901, red and yellow sand and dust from the _allara fell in nearly every por tion of Germany, France, Austria, and Turkey, and southward over the Mediterranean, and was also reported in Southern England for the first time on record. This 'dust' is a mixture of in organic particles of quartz, mica, and clay with a considerable admixture of fragments of fresh water diatoms entirely similar to the diatoms found in the dust when the northeast llarmattan blows from the same desert. southwestward to the Atlantic and the Gulf of Guinea.
The simoom is not to be confounded with the Khamsin, which usually blows for about fifty days from the northeast over Egypt.' The Sirocco is a hot moist southerly wind, in Sicily and Italy; the Samiel is the similar hot south erly wind of Turkey; the So/ano is the hot south east wind of Spain: these may all exist without any connection with the simoom, hut on some oc casions dry simoom winds have advanced north ward from the desert and merged into the hot moist southerly winds, the Sirocco, of the north ern shores of the Mediterranean.