Page:AmJourSci 3 23 134 151-152.djvu/1

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Geology and Mineralogy

That for the highest division the term Group be used; that the term for the next lower range of subdivisions be System; for the third, Series (Section in French, Abtheilung in German); for the fourth, Stage; that for the lowest, Assise or Couche in French. Formation was not adopted for either of the higher subdivisions because it is so often used with reference to mode of origin, and also for rocks of a kind without reference to age; and Terrain, because it could not be introduced into the German and Russian languages. By the above, the science will have a Paleozoic group, a Silurian system, a Trenton series, and so on.

The corresponding terms having reference to time in geological history that were recommended by the Congress are, in descending order, Era, Period, Epoch, Age. The position of the subdivision Age is not well chosen. In English if it is desired to express the idea of indefinite time, we say the ages of the past—periods having limits, and epochs being strictly times of the occurrence of particular events; and it is hence hardly practicable to apply the word Age to a subdivision of an Epoch in Geology.

It was recommended that the scale for a chart of Central Europe be 1 : 500,000. It was proposed also that in the coloring of geological maps the colors which shall be used on the geological chart of Europe be those as nearly as possible that shall hereafter be generally adopted. Rose-carmine will have the preference for the crystalline schists unless shown to be of Cambrian or later age; violet for the Triassic, blue for the Jurassic, green for the Cretaceous, and yellow will be reserved for the Cenozoic group. The notation in letters on the map will be based on the Latin alphabet; the letters used will be the initials (capital) of the name of the system; and an additional letter or numeral for subdivisions of the system, the numbering starting from the oldest included subdivision. For eruptive rocks the same rule will be followed, except that the Greek letter will be employed in place of the Latin.

The directors of the International chart of Europe will meet at the extraordinary session of the Geological Society of France in 1882, and that of the Helvetic Society of Natural Sciences in 1883, in order to explain the condition of their work; and the two Committees of the International Congress will also be present.

Some general rules also with regard to nomenclature were adopted: one that priority beyond the 12th edition of Linnæus's Systema shall not have authority; and another—which will be questioned by many, though good in purpose and in its consequences—that, in future, priority for specific names shall not be irrevocably acquired unless the species shall have been not only described but also figured.

The third meeting of the Congress will be held in Berlin in 1884.

2. Notice of the discovery of a Pœcilopod in the Utica slate formation.—Through the courtesy of my friend, Rev. William N. Cleveland, of Holland Patent, Oneida County, New York, I Am. Jour. Sci.—Third Series, Vol. XXIII, No. 134.—February, 1882.