To this end careful arrangements were made and much labor and trouble undergone. The author carried his standard mercurial mountain barometer to Fort Gibbon on the Yukon in September, 1912, and compared it with the instrument belonging to the Signal Corps of the United States army at that post. A very close agreement was found in the two instruments; the reading of the one, by himself, and of the other, by the sergeant whose regular duty it was to read and record the instrument, being identical to two places of decimals at the same temperature. [Sidenote: Readings on the Summit] Arrangements were made with Captain Michel of the Signal Corps at Fort Gibbon, when the expedition started to the mountain in March, 1913, to read the barometer at that post three times a day and record the reading with the reading of the attached thermometer. Acknowledgment is here made of Captain Michel's courtesy and kindness in this essential co-operation. The reading at Fort Gibbon which most nearly synchronizes with the reading on top of the mountain is the one taken at noon on the 7th June. The reading on top of the mountain was made at about 1.50 P. M., so that there was an hour and fifty minutes difference in time. The weather, however, was set fair, without a cloud in the sky, and had been for more than twelve hours before and remained so for thirty-six hours afterward. It would seem, therefore, that the difference in time is negligible. The reading at Fort Gibbon, a place of an altitude of three hundred and thirty-four feet above sea-level, at noon on the 7th June, was 29.590 inches with an attached thermometer reading 76.5 deg. F. The reading on the summit of Denali, at 1.50 P. M. on the same day, was 13.617. The writer is greatly chagrined that he cannot give with the same confidence the reading of the attached thermometer on top of the mountain, but desires to set forth the circumstances and give the readings in his note-book records.