When the active spirit of man is directed to the investigation of nature, or when in imagination he scans the vast fields of organic creation, among the varied emotions excited in his mind there is none more profound or vivid than that awakened by the universal profusion of life. Everywhere—even near the ice-bound poles,—the air resounds with the song of birds and with the busy hum of insects. Not only the lower strata, in which the denser vapours float, but also the higher and ethereal regions of the air, teem with animal life. Whenever the lofty crests of, the Peruvian Cordilleras, or the summit of Mont Blanc, south of Lake Leman, have been ascended, living creatures have been found even in these solitudes. On the Chimborazo[71], which is upwards of eight thousand feet higher than Mount Etna, we saw butterflies and other winged insects. Even if they are strangers carried by ascending currents of air to those lofty regions, whither a restless spirit of inquiry leads the toilsome steps of man, their presence nevertheless proves that the more pliant organization of animals may subsist far beyond the limits of the vegetable world. The Condor[72], that giant among the vultures, often soared above us at a greater altitude than the summits of the Andes, and even higher than would be the Peak of Teneriffe were it piled upon the snow-crowned summits of the Pyrenees. Rapacity and the pursuit of the soft-woolled Vicunas, which herd, like the chamois, on the snow-covered pastures, allure this powerful bird to these regions. But if the unassisted eye shows that life is diffused throughout the whole atmosphere, the microscope reveals yet greater wonders. Wheel-animalcules, _brachioni_, and a host of microscopic insects are lifted by the winds from the evaporating waters below. Motionless and to all appearance dead, they float on the breeze, until the dew bears them back to the nourishing earth, and bursting the tissue which incloses their transparent rotating[73] bodies, instils new life and motion into all their organs, probably by the action of the vital principle inherent in water. The yellow meteoric sand or mist (dust nebulæ) often observed to fall on the Atlantic near the Cape de Verde Islands, and not unfrequently borne in an easterly direction as far as Northern Africa, Italy, and Central Europe, consists, according to Ehrenberg’s brilliant discovery, of agglomerations of siliceous-shelled microscopic organisms. Many of these perhaps float for years in the highest strata of the atmosphere, until they are carried down by the Etesian winds or by descending currents of air, in the full capacity of life, and actually engaged in organic increase by spontaneous self division.