tropical phenomena, [239], [240], [241], [242];

compared with single canals, [240];

convergent, [240];

avoid blue-green areas, [241];

connect with blue-green areas, [242].

Dust storms, [90], [165].

Earth, tilt of axis of, [34];

seasons on, [35];

polar caps of, [38], [41], [44], [45], [51], [54], [69];

rainfall on, [79];