The ice-covering of the water nearly obliterated all wind waves which generally impair the accuracy of staff readings made in open bodies of water. The measurement of the height upon staff of the surface of the water, as the surface rose and fell in the well-holes, was carried on with great precision, a fact which the plottings of the observations have well brought out. The observations were taken hourly; and during a large percentage of the time these were supplemented by observations taken more frequently, often at intervals of ten minutes each.
The chronometer used in connection with tidal work was compared with true Greenwich time at New York before and after the cruise to the Arctic. The comparisons showed that during this period of 461 days the average daily gain of the chronometer was 2.2 seconds.
The mean lunitidal intervals and the mean ranges of tide, together with the approximate geographical positions of the stations, are as follows:
| Station | Latitude | Longitude | HW Interval | LW Interval | Mean Rise and Fall | ||||
| ° | ´ | ° | ´ | h | m | h | m | Feet | |
| Cape Sheridan | 82 | 27 | 61 | 21 | 10 | 31 | 4 | 14 | 1.76 |
| Point Aldrich | 83 | 07 | 69 | 44 | 7 | 58 | 1 | 50 | 0.84 |
| Cape Bryant | 82 | 21 | 55 | 30 | 0 | 03 | 6 | 22 | 1.07 |
| C. Morris Jesup | 83 | 40 | 33 | 35 | 10 | 49 | 4 | 33 | 0.38 |
| Fort Conger | 81 | 44 | 64 | 44 | 11 | 35 | 5 | 15 | 4.06 |
| Fort Conger[6] | 81 | 44 | 64 | 44 | 11 | 33 | 5 | 20 | 4.28 |
The harmonic constants for these places will be given in a paper on Arctic Tides about to be issued by the Coast and Geodetic Survey.
As indicated by its name, a "lunitidal interval" is the time elapsing between the passage of the moon across the meridian of the place or station and the occurrence of high or low water. If two stations have the same longitude, then the difference between the lunitidal intervals for the two stations denotes the difference in the times of occurrence of the tides. If they have not the same longitude, then the intervals must be converted into lunar hours (1 lunar hour = 1.035 solar hours) and increased by the west longitude of the stations expressed in hours. The result will be the tidal hours of the stations expressed in Greenwich lunar time. The difference between the tidal hours for two stations will be the difference in the time of occurrence of the tides expressed in lunar hours.
One of the most important results brought out from the tidal observations of the expedition is the fact that high water occurs two hours earlier (in absolute time) at Cape Columbia than at Cape Sheridan. The Cape Columbia tides are even earlier than the tides along the northern coast of the Spitzbergen Islands. These facts prove that the tide at Cape Columbia comes from the west. It is the Baffin Bay tide transmitted, first, northwesterly through the eastern portion of the Arctic Archipelago to the Arctic Ocean, and then easterly along the northern coast of Grant Land to Cape Columbia. That the tide wave should be felt after a passage of this kind, instead of practically disappearing after entering the Arctic Ocean, is one argument for the existence of a waterway of limited width to the northwest of Grant Land. This suggests that Crocker Land, first seen by Peary on June 24, 1906, from an altitude of about 2000 feet, may form a portion of the northern boundary of this channel or waterway.
The tides along the northern coast of Greenland are due mainly to the large rise-and-fall occurring at the head of Baffin Bay. The Arctic Ocean being of itself a nearly tideless body so far as semidaily tides are concerned, it follows that the time of tide varies but little as one goes through Smith Sound, Kane Basin, Kennedy Channel, and Robeson Channel; in other words there exists a stationary oscillation in this waterway. The northeasterly trend of the shore line of Peary Land beyond Robeson Channel and the deflecting force due to the earth's rotation tend to preserve, far to the northeastward and partly in the form of a free wave of transmission, the disturbance resulting from the stationary oscillation in the straits. The tide observations indicate that this disturbance is felt as far as Cape Morris Jesup, where the semidaily range of tide is only 0.38 foot. At Cape Bryant, northeast of Robeson Channel, the range is 1.07 feet. These values, taken in connection with the Robeson Channel disturbance, indicate that the time of tide along the coast of Peary Land becomes later as one travels eastward from Cape Bryant.
Owing to the comparatively short distance between Cape Bryant and Cape Morris Jesup, it is probable that at the latter point the crest of the wave transmitted from the southwest will appear to arrive much earlier than will the crest of the wave passing between Spitzbergen Islands and Greenland. In this way the small size of the semidaily tide at Cape Morris Jesup, as well as its time of occurrence, can be partially explained.