ScientificAmerican1921-01-29.jpg Scientific American 1921-01-22ThumbnailsScientific American 1921-02-05Scientific American 1921-01-22ThumbnailsScientific American 1921-02-05Scientific American 1921-01-22ThumbnailsScientific American 1921-02-05Scientific American 1921-01-22ThumbnailsScientific American 1921-02-05

The motor sled versus the dog sled in the frozen north. Also, "Power in big packages" and "The Mississippi's mouth".