Humboldt library of science. no. 99, 1888, Número 99Humboldt Publishing Company, 1888 |
Términos y frases comunes
action America animals Arctic avalanche bones breeding Bunsen burner burner burning candle carbonate of lime carbonic acid caverns caves climate coal-gas cold color combus combustion contained crystals Darwin Double number earth Edward Clodd ence Essays Europe evaporation excavations existence fact falls feet flame gasses Gerald Molloy gradually Grant Allen heat Heligoland Herbert Spencer Huxley hydrogen ignited Illustrated inches instinct islands J. F. C. Hecker latitudes leave less light limestone luminosity magnet mass melted migration migratory birds mountains nature nest nitrogen observed origin oxide oxygen particles pass perpetual snow Pliocene present produced Prof quantity rays regions remains routes salts Science scientific season seen snow-line solid rock sometimes species spring stalactites stalagmite stone stream substance summer supposed surface swallow T. H. Huxley tain tallow temperature theory tion tube William Kingdon Clifford wing winter wonderful zone
Pasajes populares
Página 21 - ... would at last become hereditary, and so fixed as to be what we term an instinct. It will probably be found that every gradation still exists in various parts of the world, from a complete coincidence to a complete separation of the breeding and...
Página 21 - It appears to me probable that here, as in so many other cases, ' survival of the fittest ' will be found to have had a powerful influence. Let us suppose that in any species of migratory bird, breeding can, as a rule, be only safely accomplished in a given area; and further, that during a great part of the rest of the year sufficient food cannot be obtained in that area. It will follow that those birds which do not leave the breeding area at the proper season will suffer, and ultimately become extinct,...
Página 15 - He comes ! He comes ! who loves to bear Soft sunny hours, and seasons fair;— The swallow hither comes to rest His sable wing and snowy breast.
Página 22 - Thus, to quote from the essay : " During the long course of ages, let valleys become converted into estuaries, and then into wider and wider arms of the sea ; and still I can well believe that the impulse [originally due to seeking food] which leads the pinioned goose to scramble northward, would lead our bird over the trackless waters ; and that, by the aid of the unknown power by which many animals (and savage men) can retain a true course, it would safely cross the sea now covering the submerged...
Página 24 - These avantcourriers are supposed to consist of barren birds, odd birds who have been unable to find a mate, or birds whose nests have been destroyed too late in the season to allow of a second nest to be made. Having nothing else to do, the hereditary instinct to migrate not being checked by the parental instinct, they yield to its first impulses, and drift southwards before the general body of their species. When the period of migration sets in in earnest, astounding as the fact is, it is nevertheless...