ossible. So here we were, only a few
miles from our destination, yet prevented by an impalpable and unknown
obstacle from reaching it!

We consulted together, but could find no solution of the mystery of this
invisible barrier to our progress. Then John suggested that, as we could
not go straight on, we should try a different course. So M'Allister
altered our course a few points, and once more put on the speed power,
only to be brought to a standstill again after a very short spurt.

"My word!" he exclaimed, "I'll not be beaten like this. I've driven an
old iron tramp-steamer through scores of miles of thick seaweed out in
the tropics, although the machinery was almost worn out and the engines
leaking at every joint. Here goes for full speed ahead!" he cried; and,
so saying, he switched on full power, quite heedless of my shout of "Do
be careful, M'Allister, or we shall all be smashed to pieces!"

"She's got to go!" he replied grimly, "smash or no smash! I never was
beaten yet when pushing my way through obstacles, and I'm too old a hand
to be beaten now!"

However, he found he was beaten this time, for although he switched on
the utmost power, it refused to give any evidence of its existence, and
we had to rely on our neutral power in order to maintain our position in
the air; though, as events proved, we could not have fallen.

The excitement and tension of the work had thrown M'Allister into a
profuse perspiration; and, as he stood moodily mopping his brow with his
handkerchief, I heard him muttering and swearing softly to himself. His
blood was evidently up, for he made another desperate attempt to get
the _Areonal_ to move forward, wrenching his switches with angry jerks,
but it all proved labour in vain.

"Well, what is to be done now, John?" I asked; "we have tried two
courses without any effect!"

"I would suggest, Professor, that we should go up higher," he replied,
"so as to enable us to try again from another altitude, then, perhaps,
we may pass above the obstacle."

"A good thought that, John!" I cried. So up we went, the machinery
working all right now, and our spirits rose as we soared higher; but,
alas! after rising a few hundred yards, the machines began to slow down,
and soon stopped altogether.

"The de'il himself must be taking a hand in this business!" exclaimed
M'Allister, "for this beats the worst experience I ever had! We can't go
up, we can't go down, and we can't go forward! Whatever c