C. Schucherl — Pre-Cambrian Nomenclature. 479 



ozoic, Mesozoic, and Cenozoic time. In this connection it may 

 be well to call attention to some conclusions by Van Hise,* 

 who states that pre-Cambrian time may represent, according 

 to some biologists, nine-tenths of geologic history since life 

 began on earth. "In some cases the volume of rock and great 

 intervening erosions represent a lapse of time which may be 

 not inaptly compared with all subsequent time. If geological 

 history were to be divided into three approximately equal 

 divisions, these divisions would not improbably be the time of 

 the Archean, the time of the clastic series between the Archean 

 and the Cambrian, and post-Cambrian." 



As it is generally admitted that pre-Cambrian time is very 

 long, the conclusion must naturally follow that the revolutions 

 and the major unconformities noted by geologists are of the 

 value that distinguish the eras one from another. The Lau- 

 rentian and Algomian granitic invasions have the value of 

 revolutions — the elevation of mountains and their removal 

 through erosion — and the major unconformities in the geologic 

 succession must be the places that distinguish eras. These 

 unconformities are altogether too pronounced to be representa- 

 tive of the breaks that distinguish periods. 



The next point of importance is, what shall be indicated in 

 the term or terms to be used for the era or eras back of the 

 Paleozoic? The strata of post-Cambrian time are usually 

 replete with fossils, and their primary value in geologic chro- 

 nology is accepted by all geologists. For this reason the 

 Greek ending -zoic, meaning life, has long been acceptable 

 for the Paleozoic, Mesozoic, and Cenozoic eras. Again, it is 

 admitted by nearly everyone that life existed long before the 

 Cambrian and there are leaders, as for instance Chamberlin, 

 who hold that it was present even before the Coutchiching at 

 the base of the Archeozoic. Therefore why should not all era 

 terms have the ending -zoic, as Archeozoic and Proterozoic ? 

 The writer regrets to learn from so good a teacher as Lawson 

 that he questions " the advisability of teaching visions to begin- 

 ners in geology." It is true that pre-Cambrian life is not yet 

 well enough known to be the basis of chronology, nor will it 

 seemingly ever be, but what harm can there be in the visions 

 of primitive life that are brought to mind by the terms Arche- 

 ozoic and Proterozoic ? Is it not far better to bring up these 

 visions founded on such knowledge as we have, than to suggest 

 eras barren of life by the use of the non-committal terms 

 Archean and Eparchean ? Until more reasonable evidence is 

 forthcoming, the writer prefers to adopt terms for all eras that 

 end in -zoic. 



Let us now examine the various terms that have been pro- 

 *C. R. Van Hise, Bull. 86, U. S. Geol. Surv., 1892, 491. 



