geological and ethnographical collections, the geographical and meteorological observations, and other results of the expedition.
Considering such material mainly as requisite means for investigation and for comparative study, Ehrenberg now applied himself with unceasing zeal and diligence to his rich collections, assisted by eminent scholars and artists, for the illustration of microscopical objects. The results were published during the years 1828-1830, in a volume entitled "Scientific Travels through Northern Africa and Western Asia, by Ehrenberg and Hemprich," and in a series of elaborate, strictly scientific works, written in the Latin language, with more than eighty splendid illustrative plates, the principal ones being the following: "Symbolæ physicæ, seu icones et descriptiones mammalium" (1828), "Symbolæ physicæ avium" (1828), "Symbolæ physicæ insectorum" (1829-1834), "Symbolæ physicæ animalium evertebratorum sepositis insectis" (1829-1831).
The continuation of these consummate researches and labors was interrupted for about one year, when in 1829 Alexander von Humboldt, Ehrenberg, and Gustav Rose, on invitation of the Russian Government, undertook an expedition to the Ural and Altaï regions, with the special aim of exploring their mineral resources. After the return from this exploration, Ehrenberg entered upon the most fruitful epoch of his labors and career: he accepted a professorship at the Berlin University, but still continued his original researches with unceasing assiduity. His first publications had already attracted the attention of the learned throughout Europe, and secured for the young investigator a reputation among the remarkable array of savants then in Berlin. When that severe critic, Cuvier, in 1830, presented Ehrenberg's first publications to the "Institute of France," he accompanied them with these words: "Ces découvertes changent entièrement les idées et renversent surtout bien des systèmes, elles sont du nombre de celles qui font époque dans les sciences."
The continuous series of publications founded on and recording his discoveries and researches, had reference principally to such problems and objects as the phosphorescence of the ocean, corals, fossil as well as living deposits of minute organic remains in the strata of the earth's crust, the minute organic life in the atmosphere, the phenomena of blood rain and snow, dust-showers and the "Bleeding Host," which latter one, during the middle ages, was the cause of the most barbarous excesses of the Inquisition. All these investigations and works were followed by his splendid exploration, beginning with 1840, of the minute organic creation, and by the disclosure of the influence of that "realm of littleness" in the development of the present condition of the earth's crust, and on the whole organic life of nature.
In consummate generalizations he laid down the results of his life-long, profound, and comprehensive observations and researches in the most famous of his many works, "Microgeology" (1854). Henceforth
