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mark or distinguish the divisions one from another, as a scale it is one and continuous, the parts or divisions of the scale come up to each other and are in a regular succession, but they cannot, from the nature of the scale itself, overlap or duplicate each other. Uniformity in nomenclature, and definite well-known standards and limits, and accepted means of recognizing each division for universal use, are essential to the perfection of this time-scale. In all geological literature only one name should be applied to each subdivision of the time scale, and there should be recognized for each of the grander divisions a prime standard, in some particular place on the earth, whose marks may be examined with closer and more minute discrimination as the science develops in precision. Further, in each continent we need separate standards which shall be compared as accurately as possible with the prime standard, so that each continent may have its typical geological time-scale, in concrete form, with which local formations may be corrected.

The above applies, however, only to the time-scale; the list of geological formations is a totally different thing; there is no universal uniformity of geological formations; to attempt to apply a single set of names to them is always more or less to cramp and distort the facts. Geological formations are local affairs, and to restrict geological classification to a single formation scale is to hide-bind the progress of science. There may be as many formation scales as there are examined sections of stratified rocks, and we know that all the marks by which a formation may be defined constantly vary, so that the definition of a formation, small or great, is not alike for any ten miles of its extent, and often ten feet of extension will show clear marks of difference.

Thus we see that there are two distinct sets of facts with which the geologist has to deal, and the United States Geological Survey has clearly recognized this truth in giving rules for the definition and naming of geological formations, independent of time relations, which are left for the more deliberate determination of the paleontologists. It is not, however, in the new work so much as in the revision of old standards that the appli-