Now, the tables accessible to the writer do not work out their calculations beyond eighteen thousand feet, and he confesses himself too long unused to mathematical labors of any kind for the task of extending them. He was, therefore, constrained to fall back upon the kindness of Mr. Alfred Brooks, the head of the Alaskan Division of the United States Geological Survey, and Mr. Brooks turned over the data to Mr. C. E. Giffin, topographic engineer of that service, to which gentleman thankful acknowledgment is made for the result that follows. [Sidenote: Fort Gibbon and Valdez as Bases] Ignoring a calculation based upon a temperature of 20 deg. F. on the summit, and another based upon a temperature of 13.5 deg. F. on the summit (the mean of the air temperature and that recorded for the attached thermometer) and confining attention to the calculation which takes the air temperature of 7 deg. F. as the proper figure for the correction of the barometer, a result is reached which shows the summit of Denali as twenty-one thousand and eight feet above the sea. It should be added that Mr. Giffin obtained from the United States Weather Bureau the barometric and thermometric readings taken at Valdez on 7th June about the same length of time after our reading on the summit as the reading at Gibbon was before ours. From these readings Mr. Giffin makes the altitude of the mountain twenty thousand three hundred and seventy-four feet above Valdez, which is ten feet above the sea-level. From this result Mr. Giffin is disposed to question the accuracy of the reading at Gibbon, though the author has no reason to doubt it was properly and carefully made. Valdez is much farther from the summit than Fort Gibbon and is in a different climatic zone. The calculation from the Valdez base should, however, be taken into consideration in making this barometric determination, and the mean of the two results, twenty thousand six hundred and ninety-six feet, or, roundly, _twenty thousand seven hundred feet_, is offered as the contribution of this expedition toward determining the true altitude of the mountain. The figures of Mr. Giffin's calculations touching the altitude of this mountain and also determining the altitudes of various salient points or stages of the ascent of the mountain are printed below: DENALI (MOUNT McKINLEY) USING AIR THERMOMETER READING +7 deg. AND THE READING AT FORT GIBBON FOR SAME DATE Mount McKinley, barometric reading 13.617 in. Barometer reduced to standard temperature +.027 " Temp. 7 deg. ------ 13.644 in. Fort Gibbon, barometric reading 29.590 in. Barometer reduced to standard temperature -.128 " Temp. 76.5 deg. ------ 29.462 in.