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at Dorpat, St. Petersburg, and Moscow; of Brussels, where the little Belgian state has made liberal expenditures for its iguanodons, mososauri, and hainosauri; and of Haarlem, in Holland, where the Jeyler Museum is being enriched every year with new paleontological curiosities; of Switzerland, which is not behind any country in the zeal with which it cultivates science; and of Italy, where science has its share in the revival which all departments of the intellectual life are enjoying. But I have said enough to show that paleontology is cultivated and held in high regard in Continental Europe, and that we Frenchmen also should not be indifferent to the questions of the origin and development of life.—Translated for the Popular Science Monthly from the Revue Scientifique.


By Professor H. P. ARMSBY.

THE production of nitrates during the decay of nitrogenous organic matter under suitable conditions of moisture, aëration, and temperature, is a reaction of no little importance both technically and agriculturally: technically, as the sole natural source of saltpeter; agriculturally, on account of the fact that the nitrates formed in the soil constitute the chief if not the only supply of nitrogen to the plant. But, while the conditions of nitrification have long been well known, it is only within the past eight or nine years that its true cause has been recognized. Pasteur, in 1862, appears to have first pointed out the similarity of nitrification to the various oxidations of organic matter known to be effected by the agency of mycoderms, and of which the acetic fermentation is the typical example.

In 1873, A. Müller[1] advanced the opinion that nitrification was due to the action of a ferment. He based his opinion the fact upon that solutions of pure ammonium salts and of urea are very stable, while the same bodies in sewage are rapidly nitrified, holding that the difference was due to the presence of a ferment in the latter case. In 1877 Schloesing and Müntz[2] published the results of experiments which indicated that Pasteur's suggestion and Müller's opinion were correct, and that nitrification might really be classed as a fermentation. These experimenters were engaged in investigating the oxidizing effect of the soil upon sewage. They filled a glass tube one metre long with a mixture of quartz, sand, and a small quantity of powdered limestone, and caused sewage to filter slowly through this artificial soil, so that it occupied eight days in passing through the tube. For twenty days the sewage passed through unaltered. Then nitrates began to appear

  1. "Landw. Versuchs-Stationen," xvi, p. 273.
  2. "Comptes Rendus," lxxxiv, p. 301.