Mr. Spencer's opinion, carefully considered and expressed eighteen months afterwards, will be read with real interest:--
"The distance from Dane's Island to the Pole is about 750 miles, and to Alaska on the other side about 1,500 miles. The course of the balloon, however, was not direct to the Pole, but towards Franz Josef Land (about 600 miles) and to the Siberian coast (another 800 miles). Judging from the description of the wind at the start, and comparing it with my own ballooning experience, I estimate its speed as 40 miles per hour, and it will, therefore, be evident that a distance of 2,000 miles would be covered in 50 hours, that is two days and two hours after the start. I regard all theories as to the balloon being capable of remaining in the air for a month as illusory. No free balloon has ever remained aloft for more than 36 hours, but with the favourable conditions at the northern regions (where the sun does not set and where the temperature remains equable) a balloon might remain in the air for double the length of time which I consider ample for the purpose of Polar exploration."
A record of the direction of the wind was made after Andree's departure, and proved that there was a fluctuation in direction from S.W. to N.W., indicating that the voyagers may have been borne across towards Siberia. This, however, can be but surmise. All aeronauts of experience know that it is an exceedingly difficult manoeuvre to keep a trail rope dragging on the ground if it is desirable to prevent contact with the earth on the one hand, or on the other to avoid loss of gas. A slight increase of temperature or drying off of condensed moisture may--indeed, is sure to after a while--lift the rope off the ground, in which case the balloon, rising into upper levels, may be borne away on currents which may be of almost any direction, and of which the observer below may know nothing. As to the actual divergence from the wind's direction which a trail rope and side sail might be hoped to effect, it may be confidently stated that, notwithstanding some wonderful accounts that have gone abroad, it must not be relied on as commonly amounting to much more than one or, at the most, two points.
Although it is to be feared that trustworthy information as to the ultimate destination of Andree's balloon may never be gained, yet we may safely state that his ever famous, though regrettable, voyage was the longest in duration ever attained.
At the end of 48 hours his vessel would seem to have been still well up and going strong. The only other previous voyage that had in duration of travel approached this record was that made by M. Mallet, in 1892, and maintained for 36 hours. Next we may mention that of M. Herve, in 1886, occupying 24 1/2 hours, which feat, however, was almost equal led by the great Leipzig balloon in 1897, which, with eight people in the car, remained up for 24 1/4 hours, and did not touch earth till 1,032 miles had been traversed.
The fabric of Andree's balloon may not be considered to have been the best for such an exceptional purpose. Dismissing considerations of cost, goldbeaters' skin would doubtless have been more suitable. The military balloons at Aldershot are made of this, and one such balloon has been known to remain inflated for three months with very little loss. It is conceivable, therefore, that the chances of the voyagers, whose ultimate safety depended so largely upon the staying power of their aerial vessel, might have been considerably increased.
One other expedient, wholly impracticable, but often seriously discussed, may be briefly referred to, namely, the idea of taking up apparatus for pumping gas into metal receivers as the voyage proceeds, in order to raise or lower a balloon, and in this way to prolong its life. Mr. Wenham has investigated the point with his usual painstaking care, and reduced its absurdity to a simple calculation, which should serve to banish for good such a mere extravagant theory.
Suppose, he says, the gas were compressed to one-twentieth part of its bulk, which would mean a pressure within its receiver of 300 lbs. per square inch, and that each receiver had a capacity of 1 cubic foot, while for safety sake it was made of steel plates one-twentieth of an inch thick, then each receiver would weigh 10 lbs., and to liberate 1,000 feet clearly a weight of 500 lbs. would have to be taken up. Now, when it is considered that 1,000 cubic feet of hydrogen will only lift 72 lbs., the scheme begins to look hope less enough. But when the question of the pumping apparatus, to be worked by hand, is contemplated the difficulties introduced become yet more insuperable. The only feasible suggestion with respect the use of compressed gas is that of taking on board charged cylinders under high pressure, which, after being discharged to supply the leakage of the balloon could, in an uninhabited country, be cast out as ballast last. It will need no pointing out, however, that such an idea would be practically as futile as another which has gravely been recommended, namely, that of heating the gas of the balloon by a Davy lamp, so as to increase its buoyancy at will. Major Baden-Powell has aptly described this as resembling "an attempt to warm a large hall with a small spirit lamp.'
In any future attempt to reach the Pole by balloon it is not unreasonable to suppose that wireless telegraphy will be put in practice to maintain communication with the base. The writer's personal experience of the possibilities afforded by this mode of communication, yet in its infancy, will be given.
