President's Address. 7 
representing the pre-Cambrian nucleus of the continent, 
round which the Paleozoic rocks were laid down in 
apparently regularly succeeding zones or belts. Similarly 
in the Old World it might be held that the pre-Cambrian 
nucleus of Europe is to be found in the ridge of Archean 
rocks running from the North of Ireland through North- 
Western Scotland to Scandinavia, and that the present con- 
tinent was in the main built up in a shallow sea lying to the 
south-east of this ridge, the denudation of which directly 
furnished the materials for the formation of the older 
Palaeozoic deposits. 
It will be observed that this view is rather one of the 
permanence of the continents during Cambrian and post- 
Cambrian times, than it is a theory of the permanence of the 
ocean-basins. Moreover, it must be borne in mind that what 
Dana means by “continental permanence” is (to use his own 
words) “not the absence of deep subsidences, or of deep con- 
tinental waters at times—say 2000 or 3000 feet in the 
interior or on the borders—but the non-occurrence of 
oceanic depths and alternations with oceanic conditions.” 
In other words, Dana merely asserts that there is no proof 
that the North American continent was at any period of 
post-Archeean time occupied in part or wholly by a “deep 
sea’ in the modern hydrographer’s sense of this term. Even 
in this limited sense, Dana’s view clearly begs the question, 
since the discovery of Radiolarian cherts (such as have been 
recently found in California) would at any time destroy his 
hypothesis as one of universal application. 
In any case, the apparently regular succession of the 
Paleozoic rocks in zones round Archean nuclei is by no 
means necessarily to be interpreted as done by Dana. The 
mere fact of the presence of marked unconformities in the 
Paleozoic series is sufficient to prove this. Nor, again, have 
we any definite proof that the presently visible Archean 
exposures of North America and Europe really do represent 
the nuclei of their respective continents. It is not, indeed, 
likely that they do represent such continental nuclei, for to 
establish this view it would be necessary to prove that they 
had never been deeply submerged in post-Archean time. 
