These tidal observations of the expedition of 1908-09 were the farthest north of all continuous series ever recorded anywhere, though similar observations had been taken by the Lady Franklin Bay Expedition at Fort Conger, about sixty miles southwest.
Marvin and Borup, during the November moon, continued the tidal observations at Cape Sheridan.

The tidal igloo, which was built on the ice just inside the tide crack, about one hundred and eighty yards from the ship, was an ordinary Eskimo snow igloo and was used as a protection to the men in taking the observations at the tide staff.

This staff, about twelve feet long, was driven into the bottom, and its length was marked off in feet and inches.

As the tide rose and fell, the ice and the igloo moved with the water, but the staff remained stationary, and by the position of the ice upon the staff we measured the tides, varying with the day, the moon and the season.
The tides along the north coast of Grant Land are remarkable for the slightness of the rise and fall, which varies from an average of 1.8 feet at Cape Sheridan to .8 at Cape Columbia.

As is well known to navigators, the tides at Sandy Hook, New York, sometimes rise twelve feet, while the tides in the Bay of Fundy are often over fifty feet; in Hudson Strait they are about forty, and there are places on the coast of China where the extreme rise is even greater.
The two Eskimo women were sent to Cape Columbia with MacMillan's party because the Eskimo men like to have their families with them when they go on long trips.