ILLUSTRATIONS 



Part of the Milky Way 1 



Dome of the 60-inch Reflecting Telescope at Mount Wilson Solar 



Observatory .......... 2 



Mars . . ' 4 



Three Views of Saturn 4 



Halley's Comet 5 



Diagram of the Solar System . . . . . . . .6 



A Biplane 9 



Three Forces in Play 11 



Surface of the Moon . . . . . . . . . .12 



High Tide in Nova Scotia . . . . Y . . . .13 



Low Tide at the Same Place . . . . u . . . 13 



The Phases of the Moon . . 14 



Mount Everest . . . . . . . . . . .17 



The Himalaya Mountains 19 



A Cottage in the Scotch Highlands . . . . . . .20 



Medieval Idea of the Universe ........ 22 



A Laplander's Hut C ... 25 



The Path of the Earth around the Sun . . , . . . . 26 

 A Hut in the Tropics . . . . . * . . . .27 



Magnetic Crane 38 



Transformation of Energy ........ 46 



Thermograph ........... 51 



Hot Water Furnace . . .. . .... . . .55 



A Lake Mirror ........... 59 



A Reflection Engine . . 63 



Old Sea Beaches, San Pedro 69 



Old Rock Beach, Imperial Valley, California 70 



Salt Works on the Shore of the Salton Sea 71 



Corals . . . , 74 



Granite . . . . , . .- 76 



Fossil-bearing Limestone . 76 



Conglomerate .... . . . . . . .-77 



Oil Wells . . . y . 78 



Gneiss 79 



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