Some notes on the oxygen question
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Judging Mallory & Irvine’s chances for a summit success depends to a large degree on the oxygen supply available to them.
After deciding to make a further attempt with oxygen, Mallory & Irvine had climbed to C4 on June 4, stopping en route to pick an unspecified number of oxygen cylinders from a dump (Irvine, p. 111). It is unknown how many bottles they had been carrying themselves – probably a total of 2 or 4. It is also unknown whether the two accompanying porters also carried an oxygen set and bottles.
The bottles picked from the depot were carried to C4 by five porters on June 5 (see C4 diary and note from G. Bruce quoted under 1.). Because of their weight and the restriction of a porter’s load, no porter should have carried more than 3 bottles, thus resulting in a total number of 15 or less.
The last image taken of Mallory & Irvine leaving the North Col on June 6 shows both climbers carrying oxygen apparatus. Odell wrote that both carried 2 bottles each, although in Mallory’s case only one bottle is clearly discernible. Porters’ loads are described as containing bedding, provisions and spare oxygen cylinders (Norton 4, p. 125). This is confirmed by another note found on Mallory’s body in 1999. Among the listed items are 6 bottles of oxygen.
Four (4) porters accompanied Mallory & Irvine on their climb from C5 to C6 on June 7. Above C4, a porter’s load was restricted to 9 kg (20 lbs.; see Norton 4, p. 102) – so none of the porters probably carried more than 2 bottles (16 lbs.). The carrying capacity of the party thus approximates the load listed on Mallory’s note: 3 porters for 6 bottles of oxygen plus 1 porter for provisions and other equipment from C 5. At most the porters could have carried a total 8 bottles, leaving 16 lbs. for additional equipment and provisions.
The key points of Mallory’s plan, as discussed with Norton (see 3.2) had thus been accomplished: The porters had carried a maximum number of oxygen cylinders to C6 – 6 or perhaps even 8 -, and Mallory & Irvine had used “practically no oxygen up to Camp VI” – ¾ of one bottle each. As Mallory & Irvine had carried 3 or 4 bottles themselves, this would have added 1 or 2 more to the total supply at C6.
A total supply of 8 to 10 bottles would have been sufficient for a full-scale oxygen attempt at the
summit, using 3 cylinders per climber. Even then, they would still have had 1 bottle each for sleeping
and perhaps also replacements for leaking cylinders.
But the ascent to C6 with little oxygen and the carry of 2 bottles prompted two conclusions from Mallory, which had a bearing on his plans for the summit climb as noted to Odell (see 3.):
- a) at this altitude, even 2 bottles were a “bloody load for climbing”
- b) as they had been able to climb to C 6 using little oxygen, they could save weight and go for the summit with only 2 bottles instead of 3
To this date, we know approximately how many oxygen bottles had been available to Mallory & Irvine prior to their summit bid. Mallory’s note to Odell indicated how many bottles they “probably” used.
We don’t know yet how many oxygen bottles Mallory & Irvine ended up using. However, at one point during the ascent to C6 Mallory wrote down the numbers and corresponding filling pressures of five (5) bottles on a letter envelope, which was found with his body in 1999 (see Mallory’s oxygen notes on the envelope © Mallory & Irvine Research Expedition; from Ghosts of Everest, p. 162). The notes would have shown him how long each bottle was to last.
Five bottles is probably too small a number to refer to the supply picked from the dump at the base of the North Col on June 4. The number also doesn’t correspond to the later porters’ load of six (6). Perhaps it is also of significance that Mallory wrote down this important data on the envelope of a personal letter he carried with him – and not, like his other notes, on a page of his diary, the whereabouts of which remain (to my knowledge) unknown and it was probably left behind at C5 or 6.
The strongest evidence that the five bottles noted on the envelope referred to the supply for Mallory & Irvine’s summit day is the fact that one of the listed bottles – No. 9 – was found in 1999 high on the Northeast Ridge at c. 8420-8475 m/27,626-27,806 ft.
Did Mallory opt for a compromise on summit day and had Irvine carry 3 bottles, while he took just 2 as indicated in his note to Odell?
What conclusion can be drawn about Mallory’s plans for the final ascent when this tactic would eventually have left the two climbers with just one full bottle of oxygen between them? Did Irvine adopt more of a porter’s role – and did Mallory consider the possibility of a solo ascent for the final stage of the climb?