rs a day in that little compartment, though it will not
be necessary to take the eight hours continuously, for we may spend a
few intervals in the other rooms.

"John and I will take general charge of the machinery in that room, and
he will also look after your machines whilst you are with me in our
Martian air-chamber. In addition to these arrangements, we have prepared
a concentrated air of the same kind which we can carry about with us in
bottles, so that by simply opening a little valve in the bottle we can
inhale some of the air now and then when we are in the other rooms. By
adopting this plan, I hope when we reach Mars we shall all have become
so acclimatised that we shall be able to breathe the Martian air without
much inconvenience."

"Heh, Professor," said M'Allister, "what a mon you are for planning
things out; I would never have thought of that!"

"John had quite as much to do with the planning out as I had," I
replied; "and as you now understand what we propose to do, we will at
once commence our training, but we shall not feel much difference in the
air for the next day or two."

We accordingly put our plan into operation, each of us making up at
least eight hours' time every day in the Martian air-chamber, with the
result that we gradually became accustomed to the thinner air, and could
breathe it without any feeling of inconvenience.

As the days went on I began to notice that John was becoming very
irritable; and so was I, though to a lesser extent. The closer
confinement to one room was evidently beginning to tell upon us, and day
by day the effects were more apparent on both of us, especially in the
case of John; but, strangely enough, whilst we were becoming more
depressed and irritable, M'Allister's spirits seemed to be rising every
day!

It has often been remarked that if two or three people are shut up
together for a considerable time, with no other companionship or change,
sooner or later they are bound to fall out with each other.

Up to the present we had all agreed splendidly, but now John's
irritability seemed to increase hourly; and as regards myself, I often
found it necessary to exercise very great self-control to avoid giving
very sharp and snappish answers to John's peevish and querulous remarks.

But the inevitable explosion came at last, and, like all explosions, was
very sudden and unexpected when it did happen.

All the morning of the 2nd of September John had been wanderin