Precipitation, 51, 79, 154, 155; effect on glaciation, 52. Presentation, a, defined, 287, 288. Probability, law of, 160. Projections on the terminator, 77, 81, 96, 100, 104, 165; color of, 102; cause of, 104-107; great one of 1903, 101-104; of 1900, 104. _Propontis_, the, 242; canals in, 247; oases in, 256. _Protonilus_, association with Luci Ismenii, 260. _Pseboas Lucus_, 207, 250, 253, 263; anomalous position of, 262. Quaternary epoch of the Earth, 137. Reddish-ochre regions, 153, 155; deserts, 149, 156, 163; variations of tint in, 32, 148, 149, 151. Rifts in polar cap, 61-63, 67, 162, 325-329; permanent in place, 61, 62; not depressions, 62, 63, 162; coincide with canals, 326-328; explanation of, 328, 329. Rotation, early noted, 108, 109; how determined, 34; time of, 34, 160; disclosed by markings, 32-34, 108. _Sabaeus Sinus_, 23, 207, 268, 269. San Francisco Peaks, 18, 19, 149, 379, 380. Saturn, 33. Scepticism, 27, 28, 204. Schaeberle, 30. Schiaparelli, 11, 15, 21, 23, 24, 26, 27, 29, 30, 31, 34, 68, 74, 75, 81, 114, 115, 120, 121, 173, 177, 186, 192, 212, 217, 221, 247, 249, 265, 282, 313, 314, 325, 337, 367, 373. Seas (see Dark Regions). southern, 92; formerly on Mars and the Moon, 129; internal absorption of, 147. Seasonal change, metabolic, 169; in canals, 168, 169, 285, 373. Seasons, like our own, 34, 35, 166; length of, 48, 79, 161; of vegetal growth, 346, 347. Secular change, in canals, 314. Silurian era of the Earth, 134, 138, 140. Sky, blotting out of, 14; measure of extinction of, 16. Sky, Martian, 89; clear, 165. Slipher, 101, 103. Snow, 345; limits of, on Earth and Mars, 108. _Solis Lacus_, 23, 242. Spring, Martian, 35, 48; haze in, 94. S.S. Challenger, concerning south polar cap of earth, 45. S.S. Pagoda, 45. Subsidiary snow patches, 67, 73. Summer, Martian, length of, 35, 48, 381. Surface, relatively flat, 62, 76, 97, 164; covered by canal network, 243; clear-cut in good air, 258; in fluid equilibrium, 374; indicative of thin air, 162, 167. Surface features, reality of, proved, 26, 33. _Syrtis Major_, 22; first marking made out, 23. _Tempe_, white in, 77, 80. Temperature, 78, 147, 165, 166; effect on life, 358. Terminator, projections on, 77, 81, 96, 100-107, 114, 165; depressions on, 164. Terrane, 108, 265. Terraqueousness, shown by earth, 128, 131. Terrestriality, follows terraqueousness, 129, 131, 137, 144-146; earth’s oceans contracting in size, 131; inevitably, 131, 146; as shown by Mars and the Moon, 128, 130, 131; as shown by the geologic history of earth, 131-137; as shown by paleontology, 138-144; making a better habitat, 145, 146. Tertiary times of the Earth, 137, 151.