When speaking of the Archaean hills of Missouri Pumpelly has likened them unto "an archipelago of islands in the Lower Silurian strata which surrounded them as a whole and separate them from one another." To one who knows this interesting territory with its isolated and grouped knobs hills and mountains of crystalline rocks standing out more or less prominently and dotting the broad expanse of more recent sedimentaries, this figure is an exceedingly happy one; one most admirably taken.
Proceedings of the Iowa Academy of Sciences
©1893 Iowa Academy of Science, Inc.
Lonsdale, E. H.
"Topography of the Granite and Porphyry Region of Missouri,"
Proceedings of the Iowa Academy of Science, 1(Pt. 4), 43-48.
Available at: https://scholarworks.uni.edu/pias/vol1/iss4/17