While looking for correlations between temperatures along Scott's route, which stretched for about 749 geographical miles
to the pole, the authors make a reference point using respective data simultaneously measured at the base camp at Cape Evans.
To assume that replacing either Marshall or Adams with Armytage would have allowed the party to travel an additional 194 geographical miles
(the distance to the Pole and back from the farthest south) ignores the yeoman work each did, as well as the fact that Shackleton turned back simply because the food was running out.
The United States Code clarifies that the land may be "permanently or periodically covered by tidal waters from the line of mean high tide out three geographical miles
distant from the coast or the Gulf of Mexico."  The land also may be "filled in, made, or reclaimed lands."  The United States Code excludes streambeds lawfully conveyed to private citizens.