'It's I, Lucie! Come quick: the reds have gone into the blacks' house.
Come quick!'

'And do you know the road they took?'

'Yes, I marked it.'

'What! Marked it? How?'

'I did what Hop-o'-my-Thumb did: I scattered little white stones along
the road.'

I hurried out. Things had happened as my six-year-old colleague said.
Lucie had secured her provision of pebbles in advance and, on seeing
the Amazon regiment leave barracks, had followed them step by step and
placed her stones at intervals along the road covered. The Ants had made
their raid and were beginning to return along the track of tell-tale
pebbles. The distance to the nest was about a hundred paces, which gave
me time to make preparations for an experiment previously contemplated.

I take a big broom and sweep the track for about a yard across. The
dusty particles on the surface are thus removed and replaced by others.
If they were tainted with any odorous effluvia, their absence will
throw the Ants off the track. I divide the road, in this way, at four
different points, a few feet a part.

The column arrives at the first section. The hesitation of the Ants is
evident. Some recede and then return, only to recede once more; others
wander along the edge of the cutting; others disperse sideways and seem
to be trying to skirt the unknown country. The head of the column, at
first closed up to a width of a foot or so, now scatters to three
or four yards. But fresh arrivals gather in their numbers before the
obstacle; they form a mighty array, an undecided horde. At last, a few
Ants venture into the swept zone and others follow, while a few have
meantime gone ahead and recovered the track by a circuitous route. At
the other cuttings, there are the same halts, the same hesitations;
nevertheless, they are crossed, either in a straight line or by going
round. In spite of my snares, the Ants manage to return to the nest; and
that by way of the little stones.

The result of the experiment seems to argue in favour of the sense of
smell. Four times over, there are manifest hesitations wherever the
road is swept. Though the return takes place, nevertheless, along the
original track, this may be due to the uneven work of the broom, which
has left certain particles of the scented dust in position. The Ants
who went round the cleared portion may have been guided by the sweepings
removed to either side. Before, therefore, pronouncing judgment for or
against the sense