THE HEIGHT OF DENALI, WITH A DISCUSSION OF THE READINGS ON THE SUMMIT
AND DURING THE ASCENT
The determination of the heights of mountains by triangulation is, of
course, the method that in general commends itself to the topographer,
though it may be questioned whether the very general use of aneroids for
barometric determinations has not thrown this latter means of measuring
altitudes into undeserved discredit when the mercurial barometer is used
instead of its convenient but unreliable substitute.
The altitude given on the present maps for Denali is the mean of
determinations made by triangulation by three different men: Muldrow on
the Sushitna[7] side in 1898, Raeburn on the Kuskokwim side in 1902, and
Porter, from the Yentna country in 1906. In addition, a determination
was made by the Coast and Geodetic Survey in 1910, from points near
Cook's Inlet. "The work of the Coast Survey," writes Mr. Alfred Brooks,
"is more refined than the rough triangulation done by our men; at the
same time they were much further away." "It is a curious coincidence,"
he adds, "that the determination made by the Coast Survey was the mean
which we had assumed from our three determinations" (twenty thousand
three hundred feet).
[Sidenote: Theodolites and Barometers]
There are, however, two sources of error in the determination of the
height of this mountain by triangulation--a general one and a particular
one. The general one lies in the difficulty of ascertaining the proper
correction to be applied for the refraction of the atmosphere, and the
higher the mountain the greater the liability to this error; for not
much is positively known about the angle of refraction of the upper
regions of the air. The officers of the Trigonometrical Survey of India
have published their opinion that the heights of the great peaks of the
Himalayas will have to be revised on this account. The report of the
Coast Survey's determination of the height of Denali claims a
"co-efficient of refraction nearer the truth" than the figure used on a
previous occasion; but a very slight difference in this factor will make
a considerable difference in the result.
The particular source of error in the case of this mountain lies in the
circumstance that its summit is flat, and there is no culminating point
upon which the cross-hairs of the surveying instrument may intersect.
The barometric determination of heights is, of course, not without
similar troubles of its own. The tables of altitudes corresponding to
pressures do not agree, Airy's table giving relatively greater altitudes
for very low pressures than the Smithsonian. All such tables as
originally calculated are based upon the hypothesis of a temperature and
humidity which decrease regularly with the altitude, and this is not
always the case; nor is the "static equilibrium of the atmosphere" which
Laplace assumed always maintained; that is to say an equal difference of
pressure does not always correspond to an equal difference of altitude.
There is, in point of fact, no absolute way to determine altitude save
by running an actual line of levels; all other methods are
approximations at best. But there had never been a barometric
determination of the height of this mountain made, and it was resolved
to attempt it on this expedition.
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° 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.
The note-book gives the air temperature on the summit as 7° F., taken by
a standard alcohol minimum thermometer, and it remained constant during
the hour and a half we were there. The sun was shining, but a bitter
north wind was blowing. But the reading of the thermometer attached to
the barometer is recorded as 20° F. I am unable to account for this
discrepancy of 13°. The mercurial barometer was swung on its tripod
inside the instrument tent we had carried to the summit, a rough zero
was established, and it was left for twenty minutes or so to adjust
itself to conditions before an exact reading was taken. It was my custom
throughout the ascent to read and record the thermometer immediately
after the barometer was read, but it is almost certain that on this
momentous occasion it was not done. Possibly the thermometer was read
immediately the instrument was taken out of its leather case and its
wooden case and set up, while it yet retained some of the animal heat of
the back that had borne it, and the reading was written in the prepared
place. Then when the barometer was finally read, no temperature of the
attached thermometer was noted. This is the only possible explanation
that occurs, and it is very unsatisfactory. It was not until we were
down at the base camp again that I looked at the figures, and discovered
their difference, and I could not then recall in detail the precise
operations on the summit. It is hard to understand, ordinarily, how any
man could have recorded the two readings on the same page of the book
without noticing their discrepancy, but perhaps the excitement and
difficulty of the situation combined to produce what Sir Martin Conway
calls "high altitude stupidity."
[Sidenote: In Exculpation]
It is indeed impossible to convey to the reader who has never found
himself circumstanced as we were an understanding of our perturbation of
mind and body upon reaching the summit of the mountain: breathless with
excitement--and with the altitude--hearts afire and feet nigh frozen.
What should be done on top, what first, what next, had been carefully
planned and even rehearsed, but we were none of us schooled in stoical
self-repression to command our emotions completely. Here was the crown
of nearly three months' toil--and of all those long years of desire and
expectation. It was hard to gather one's wits and resolutely address
them to prearranged tasks; hard to secure a sufficient detachment of
mind for careful and accurate observations. The sudden outspreading of
the great mass of Denali's Wife immediately below us and in front of us
was of itself a surprise that was dramatic and disconcerting; a splendid
vision from which it was difficult to withdraw the eyes. We knew, of
course, the companion peak was there, but had forgotten all about her,
having had no slightest glimpse of her on the whole ascent until at the
one stroke she stood completely revealed. Not more dazzling to the eyes
of the pasha in the picture was the form of the lovely woman when the
slave throws off the draperies that veiled her from head to foot.
Moreover, problems that had been discussed and disputed, questions about
the conformation of the mountain and the possibilities of approach to
it, were now soluble at a glance and clamored for solution. We held them
back and fell at once to our scientific work, denying any gratification
of sight until these tasks were performed, yet it is plain that I at
least was not proof against the disturbing consciousness of the wonders
that waited.
It was bitterly cold, yet my fingers, though numb, were usable when I
reached the top; it was in exposing them to manipulate the hypsometrical
instruments that they lost all feeling and came nigh freezing. And
breathlessness was naturally at its worst; I remember that even the
exertion of rising from the prone position it was necessary to assume to
read the barometer brought on a fit of panting.
[Sidenote: Calculations for Altitude]
With these circumstances in mind we will resume the discussion of the
readings taken on the summit and their bearing upon the altitude of the
mountain. It seems right to disregard the temperature recorded for the
attached thermometer, and to use the air temperature, of which there is
no doubt, in correcting the barometric reading. So they stand:
Bar. Temp.
13.617 inches 7° F.
The boiling-point thermometer stood at 174.9° F. when the steam was
pouring out of the vent.
They stand therefore:
_Gibbon_ (334 feet altitude) _The Summit of Denali_
Bar. Ther. Bar. Ther.
29.590 76.5° F. 13.617 7° F.
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° F. on the summit,
and another based upon a temperature of 13.5° 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° 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° AND THE READING
AT FORT GIBBON FOR SAME DATE
Mount McKinley, barometric reading 13.617 in.
Barometer reduced to standard temperature +.027 " Temp. 7°
------
13.644 in.
Fort Gibbon, barometric reading 29.590 in.
Barometer reduced to standard temperature -.128 " Temp. 76.5°
------
29.462 in.
Mount McKinley, corrected barometer 13.644 in. 21,324 ft.
Fort Gibbon, corrected barometer 29.462 " 400 "
------
20,924 ft.
Mean temperature, 41.7°--approximate
difference in elevation 20,924 ft. -356 ft.
Latitude, 64°--approximate difference
in elevation 20,568 " +15 "
Mean temperature, 41.7°--approximate
difference in elevation 20,568 " +71 "
Elevation lowest, 400--approximate
difference in elevation 20,568 " +20 "
------
Elevation above Fort Gibbon 20,674 ft.
Elevation of Fort Gibbon 334 "
------
_Elevation above sea_ 21,008 ft.
USING THE THERMOMETRIC READING OF 7° AT MOUNT
MCKINLEY AND THE U. S. WEATHER BUREAU READING
AT VALDEZ FOR SAME DATE
Mount McKinley, barometric reading 13.617 in.
Barometer reduced to standard temperature +.027 " Temp. 7°
------
13.644 in.
Valdez, barometric reading 29.76 in.
Barometer reduced to standard temperature .068 "
------
29.692 in. Temp. 54°
Mount McKinley, corrected barometric reading 13.644 in. 21,324 ft.
Valdez, corrected barometric reading 29.692 " 190 "
------
21,134 ft.
Mean temperature, 30.5°--approximate
difference in elevation 21,134 ft. -840 "
Latitude, 62°--approximate difference
in elevation 20,295 " +18 "
Mean temperature, 30.5°--approximate
difference in elevation 20,295 ft. +42 ft.
Elevation lowest, 190--approximate
difference in elevation 20,295 " +20 "
------
Elevation above Valdez 20,374 ft.
Elevation of Valdez 10 "
------
_Elevation above sea_ 20,384 ft.
ALTITUDES OF CAMPING STATIONS
FIRST GLACIER CAMP
Glacier Camp, barometric reading. 22.554 in. Temp. 81°
Barometer reduced to standard temperature -.106 "
------
22.448 in.
Fort Gibbon, barometric reading 29.110 in. Temp. 74°
Barometer reduced to standard temperature -.120 "
------
28.990 in.
Glacier Camp, corrected barometer 22.448 in. 7,791 ft.
Fort Gibbon, corrected barometer 28.990 " 840 "
------
6,951 ft.
Mean temperature, 77.5°--approximate
difference in elevation 6,951 ft. +393 "
Latitude, 64°--approximate difference
in elevation 7,343 " +5 "
Mean temperature, 77.5°--approximate
difference in elevation 7,343 " +74 "
Elevation lowest, 840--approximate
difference in elevation 7,343 " +3 "
------
Elevation above Fort Gibbon 7,426 ft.
Elevation of Fort Gibbon 334 "
------
_Elevation above sea_ 7,760 ft.
HEAD OF MULDROW GLACIER
Muldrow Glacier, barometric reading 19.640 in. Temp. 36°
Barometer reduced to standard temperature -.013 "
-------
19.627 in.
Fort Gibbon, barometric reading 30.065 in. Temp. 71°
Barometer reduced to standard temperature -.115 "
-------
29.950 in.
Muldrow Glacier, corrected barometer 19.627 in. 11,441 ft.
Fort Gibbon, corrected barometer 29.950 " (-)45 "
------
11,486 ft.
Temperature, 53.5°--approximate
difference in elevation 11,486 ft. +79 "
Latitude, 65°--approximate difference
in elevation 11,565 " +8 "
Mean temperature, 53.5°--approximate
difference in elevation 11,565 " +63 "
Elevation lowest, 45--approximate
difference in elevation 11,565 " +6 "
-------
Elevation above Fort Gibbon 11,642 ft.
Elevation of Fort Gibbon 334 "
-------
_Elevation above sea_ 11,976 ft.
PARKER PASS
Parker Pass, barometric reading 17.330 in. Temp. 43°
Barometer reduced to standard temperature -.023 "
-------
17.307 in.
Fort Gibbon, barometric reading 30.050 in. Temp. 69.5°
Barometer reduced to standard temperature -.111 "
------
29.939 in.
Parker Pass, corrected barometer 17.307 in. 14,861 ft.
Fort Gibbon, corrected barometer 29.939 " (-)35 "
------
14,896 ft.
Mean temperature, 56.25°--approximate
difference in elevation 14,896 ft. +185 "
Latitude, 64°--approximate difference
in elevation 15,091 " +11 "
At temperature of 56.25°--approximate
difference in elevation 15,091 " +92 "
Elevation lowest, -35°--approximate
difference in elevation 15,091 " +11 "
------
Elevation above Fort Gibbon 15,195 ft.
Elevation of Fort Gibbon 334 "
------
_Elevation above sea_ 15,529 ft.
LAST CAMP
Last Camp, barometric reading 15.220 in. Temp. 40°
Barometer reduced to standard temperature -.016 "
------
15.204 in.
Fort Gibbon, barometric reading 29.660 in.
Barometer reduced to standard temperature -.120 " Temp. 73.5°
------
29.540 in.
Last Camp, corrected barometer 15.204 in. 18,382 ft.
Fort Gibbon, corrected barometer 29.540 " 329 "
------
18,053 ft.
Mean temperature, 56.75°--approximate
difference in elevation 18,053 ft. +248 ft.
Latitude, 64°--approximate difference
in elevation 18,301 " +17 "
Mean temperature, 56.75°--approximate
difference in elevation 18,301 " +112 "
Elevation lowest, 329--approximate
difference in elevation 18,301 " +16 "
------
Elevation above Fort Gibbon 18,446 ft.
Elevation of Fort Gibbon 334 "
------
_Elevation above sea_ 18,780 ft.
FOOTNOTE:
[7] "Sushitna" represents unquestionably the native pronunciation and
the "h" should be retained. The reason for its elision current in Alaska
is too contemptible to be referred to further. Perhaps the same genius
removed this "h" who removed the "'s" from the "Cook's Inlet" of the
British admiralty. One is not surprised when a post-office at Cape
Prince of Wales is named "Wales" because one is not surprised at any
banalities of the postal department--in Alaska or elsewhere, but one
expects better things from the cultured branches of the government
service. It is interesting to speculate what will happen to
Revillagigedo Island, which Vancouver named for the viceroy of Mexico
who was kind to him, when the official curtailer of names finds time to
attend to _it_. If there be a post-office thereon it is probably already
named "Gig."