Rainbow.—A bow or arch exhibiting, in concentric bands, the several colors of the spectrum, and formed in the part of the hemisphere opposite to the sun by the refraction and reflection of the sun’s rays in drops of falling rain. Besides the ordinary bow, called also primary rainbow, which is formed by two refractions and one reflection, there is also another often seen exterior to it, called the secondary rainbow, concentric with the first, and separated from it by a small interval. It is formed by two refractions and two reflections, is much fainter than the primary bow, and has its colors arranged in the reverse order from those of the latter.
Seismology (sīs-mŏl´ô-jy̆).—The science of earthquakes.
Seismometer (sīs-mŏm´e-tẽr).—An instrument for measuring the direction, duration, and force of earthquakes and like concussions.
Simoon (sĭ-mōōn´).—A hot, dry, suffocating, dust-laden wind, that blows occasionally in Arabia, Syria, and the neighboring countries, generated by the extreme heat of the parched deserts or sandy plains.
Sirocco (sĭ-rŏk´kô).—An oppressive, relaxing wind from the Libyan deserts, chiefly experienced in Italy, Malta, and Sicily.
Sivatherium (siv-a-thē´ri-um).—A large four-horned antelope, known by fossil remains found in Pliocene rocks of Hindustan.
Strophomena (strō-fŏm´ĕ-nä).—A genus of shell-like animals similar to the nautilus, found in numerous fossil forms in Lower Silurian and the carboniferous strata.
Tornado (tor-nā´dô).—A violent whirling wind; specifically a tempest distinguished by a rapid whirling and slow progressive motion, usually accompanied with severe thunder, lightning, and torrents of rain, and commonly of short duration and small breadth; a small cyclone.
Typhoon (tï-fōōn´).—A violent whirlwind; specifically, a violent whirlwind occurring in the Chinese seas.
Wind.—Air naturally in motion with any degree of velocity; a current of air.