154 The American Geoloijisf. March, 1895 
manner, than at iirst appears. Two recent notalile efforts 
have been made to put into harmony, on a broad basis of 
classification, the rather divergent views and interpretations 
of the lake Superior region. We refer to those of Messrs. 
Walcott and Van Hise, the former in a bulletin of the United 
States Geological Survey entitled "Correlation Papers, Cam- 
brian," Bulletin No. 81, and the latter in a similar bulletin, 
entitled "Archean and Algonkian." Bulletin No. 86, the for- 
mer published in 1891, and the latter in 1892. These masterly 
summaries of the literature of these subjects are a credit to 
the U. S. Geological Survey, and will long remain standards 
of comparison for future study. But, like all human under- 
takings, they exhibit the genius and the "personal equation" 
of their authors. This can hardly be considered a fault, for 
it is a characteristic which the greatest products of the great- 
est men alw^ays manifest. Indeed, the personal stamp of the 
author goes with every advance which is made in geology, as 
well as in all departments of human progress. Every new step 
must be based on a previous step. That earlier step is the 
foundation and the governing element, not only in the direc- 
tion of the new step, but also very largely in the particular 
nature or quality which it exhibits. For this reason the va- 
rious steps of any seeker after new trutii can be interpreted 
by tracing backward the line through which the investigation 
was pursued. The steps are interpreters of each other. 
It is therefore of the utmost importance that no ^firsf step 
be taken erroneousl}^, or if erroneously, that it be retraced 
frankly and a new foundation laid in a step in the right di- 
rection, and of the right quality as to force and scope. It will 
be incumbent on the writer therefore, in the preparation of a 
series of papers on the geology of the lake Superior region, to 
enter somewhat into the history of the progress made already 
and to write what might be called a review of the two fore- 
going correlation papers. In the course of this examination it 
may appear that several false steps have been made h^ the 
authors which ought to have been retraced, but which were 
used as foundation stones foi- further advance, and that 
therefore they have arrived at faulty results. 
With the early English geologists there was perhaps as 
much difference regarding the base of the Cambrian as re- 
