ScientificAmerican1917-04-21.jpg Scientific American 1903-05-30ThumbnailsScientific American 1903-05-30ThumbnailsScientific American 1903-05-30ThumbnailsScientific American 1903-05-30ThumbnailsScientific American 1903-05-30Thumbnails
Plunging through an irrigating ditch with a continuous-tread tractor.