TABLE OF CONTENTS. vii 



on Corundum, 232 ; the Vermiculite Group of Minerals, 226 ; Discovery of 

 Coal in Spitzbergen, 236; Mineral Butter, 227; the Molecular Structure of 

 Meteoric Iron, 219 ; Atmospheric Dust, 228 ; Composition of Fulgurites, 228 ; 

 Optical Structure of Crystals, 235. 

 (b.) GEOLOGY. 



General : Relation of Man's Existence to the Glacial Period, 224 ; Struct- 

 ure of the Earth, 219; Mallet's Observations on the Properties of Rocks, 

 221 ; the Lines of Elevation in the Earth's Crust, 223 ; the Formation of 

 the Earth's Crust, 223 ; Distribution of Volcanoes, 229 ; Age of Central 

 American Gold Deposits, 230 ; New Guano Deposits in Peru, 230 ; Geology 

 of the Siberian Steppes, 235 ; Geological Collection at the Centennial Ex- 

 position, 228; Volcanoes (see also Terrestrial Physics), Distribution 

 of, 229 ; Progress of the Geological Survey of California, 225 ; of Wisconsin, 

 231 ; of Pennsylvania, 230 ; Report for 1873 of the State Geologist of New 

 Jersey, 232 ; Geological Survey of Louisiana, 232 ; Final Report upon the 

 Geology of Ohio, 234; Fifth Annual Report of the Geological Survey of 

 Indiana, 236 ; Dr. Hayden's Bulletin, 233. 



F. GEOGRAPHY (lxxvi) 237 



(a.) GEODESY, NAVIGATION, AND HYDROGRAPHY. 



An Improved Large Theodolite, 261 ; the Theory of the Uses of the Sur- 

 veyor's Level, 243 ; Errors in Trigonometrical Levelings, 251 ; Hypsometry 

 in the Rocky Mountains, 238 ; Measurement of Altitudes by the Barometer, 

 241 ; Dr. Toner's Dictionary of Elevations, 242 ; Coast-survey Measurements 

 of Meridional Lines, 237; Rohlfs' Exploration of the Libyan Desert, 259; 

 Geodesy in the Far West, 240; the Topographical Charts of Switzerland, 

 237 ; Geodesy in the Island of Corsica, 250 ; Longitude of Washington and 

 Greenwich, 244; Longitude at Sea, 244. 

 (b.) PHYSICAL GEOGRAPHY. 



Fluctuations in the Level of Lake Superior, 245 ; Saltness of the Water of 

 the Suez Canal, 257. See also Terrestrial Physics. 

 (C.) EXPLORATIONS AND RESEARCHES. 



The Ocean and its Depths : Explorations of Norwegian Seas, 253 ; Notes 

 of the Challenger's Movements, 255. 



The Arctic Regions: the Arctic Continent and Polar Sea, 252; Ger- 

 man Society for Polar Exploration, 253 ; Arctic Explorations in England, 

 253. 



North America. Alaska: Explorations of W. H. Dall, 329 ; of H.W. 

 Elliott (see also Summan r , p. lxxxvii) ; of Pinart, 246 ; Hudson's Bay T< r- 

 ritory : Horetzky on the Hudson's Bay Territory, 256 ; Rocky Mountains : 

 Professor Stoddart's Expedition to Colorado, 257 ; Explorations of Professor 

 Powell in 1874, 262; Explorations in 1874 of Lieutenant G. M. Wheeler, 

 United States Engineers, 267, 353 ; Explorations of Dr. Hayden in 1874, 

 275 ; Florida : Exploration of Lake Okeechobee, 245. Middle America : 

 Explorations of W. M. Gabb in Costa Rica, 246. South America : Pro- 

 fessor Orton's Explorations, 248; Exploration of Terra del Fuego, 257. 

 Europe : Russian Explorations in Lapland, 260. Asia : Explorations by 

 the Russian Government, 259 ; the Sources of the Irrawaddv. 261 : Explora- 



