Popular Science Monthly, 66. köide

acid aliens American animals anomodonts application atomic weight average Bermuda body cells cent century chemical chemistry chromosphere congress determine dinosaurs direction discovery disease distribution electric elements engineering evolution existence experience fact Galileo geometry give grades Harrington Sound helium hybrid immigrants important increased institutions interest investigation islands knowledge known labor laboratory land large number less lines mathematics matter means measure ment method metric system nature Niagara Niagara Falls nitrogen observations organization paleontology period Petri dish phenomena philosophy physical physiological plant practical present President probably problems Professor pronunciation proteid psychology question radial velocities radium scientific societies solar solution species spectroscopic binaries stars substances sunspots surface temperature theory thorium tion tissue to-day United University variable stars variations words