296 
HAROLD’S DISCUSSIONS. 
Potato, II, 62, 265. 
Potentilla, 267. 
Prairie-chicken (see Birds), IV, 66. 
Pre-archsean, 17. 
Pterodactyl, 68. 
Puma, IV, 191. 
Pumpkins, II, 58. 
Pumps, action of. III, 112. 
Quail (see Birds). 
Quantivalonce, IV, 278. 
Quaternary period, 74; animals of, 
76; bird forms of, 79. 
Bain, 96. 
Rainbow, II, 144; III, 169. 
Refraction (see Light), 111, 160,169. 
Regulus, 165. 
Reproduction, of ameba, 218; meth¬ 
ods of, 232; vorticella, 230. 
Reptiles, snakes, III, 87; age of, 
65. 
Rhinoceros, 76. 
Rhizopods, 218. 
River, valley explored, IV, 1. 
Rocks, Carboniferous age, 48; clay 
series, 14; Devonian age, 42; 
limestone, 34; 11,80; coal forma¬ 
tion, 50; Illinois coal mine, 50; 
corals, 34; dangers to miners, 51; 
feldspar, II, 79; laid level, IV, 
94; formations, how discovered, 
5, 35; mine, 51; “cage” in, 50; 
miner’s lamp, 50; cars in, 51; 
depth, 51; pebbles, II, 81; salt, 
35; strata, Wisconsin, 6 ; IV, 101; 
subcarboniferous age, 48; Silu¬ 
rian age, 39 ; quartz, II, 79 ; 35. 
Roots, forms, IV, 9 ; growth, IV, 6 ; 
“rising,” IV, 13; structure, IV, 
9, 16; uses, IV, 12. 
Rubber-tree, IV, 172. 
Sagittarius, 167. 
Salmon (see Fish), IV, 49. 
Salt, I, 77. 
Sandstone, series, 14 ; New Red, 65. 
Sap, IV, 17. 
Sapodilla, IV, 171. 
Saturn, 186. 
Sea, color, IV, 127 ; cucumbers, IV, 
154; horse, IV, 135; urchins, IV, 
153; weeds, green and brown 
algae, 42. 
Seal, IV, 244. 
Seed, dispersion of, I, 1-12; 267. 
Selection, 263; natural, artificial, 
266. 
Scorpio, 166. 
Scorpion, IV, 208. 
Sheep, II, 64. 
Sigillaria, 56. 
Silurian rocks, 34; life of, 36. 
Sirius, 144. 
Snail, II, 145. 
Snakes, IV, 196 (see Reptiles). 
Snow, II, 85, 97. 
Sodium, IV, 268. 
Soil, HI, 91, 101. 
Solar system, 181, 195. 
Sound, III, 118, 121. 
Species (see Struggle). 
Spectroscope, 30, 164. 
Spectrum, 157 ; of Pollux, 31. 
Spider, I, 90 ; tarantula, IV, 207. 
Sponges, IV, 155. 
Spores, 209. 
Springs, IV, 86. 
Squirrel, II, 110. 
Stars, apparent movement of, 140; 
at Poles, 142; at equator, 142; 
first magnitude, 145 ; names, 145; 
path of, 151 ; Betelguese, 163 ; 
Castor and Pollux, 165 ; shootinof- 
stars, 193 ; visit to, 195. 
