During the ascent some of us felt a kind of sea-sickness, caused partly by fatigue and partly by the rarefaction of the air. The barometer sank 140 millimetres; the air we breathed had lost one-fifth of its density, and was consequently one-fifth poorer in oxygen. By those in good condition this slight modification would pass unnoticed, but, added to the fatigue of the previous day and to want of sleep, it increased our discomfort. We mounted slowly, our legs aching, our breathing difficult. Every twenty steps or so one had to halt. At last the summit was gained. We took refuge in the rustic chapel of St. Croix to take breath and counteract the biting cold by a pull at the gourd, which this [[191]]time we emptied. Soon the sun rose. To the farthest limit of the horizon Mont Ventoux projected its triangular shadow, tinted violet from the effect of the diffracted rays. Southward and westward stretched misty plains, where, when the sun rose higher, one would distinguish the Rhône as a silver thread. On the north and east an enormous cloud-bed spreads under our feet like a sea of cotton wool, whence the dark tops of the lower mountains rise as if they were islets of scoriæ, while others with their glaciers shine glorious on the side where the Alps uplift their chain of mountains.
But botany calls, and we must tear ourselves from this magic spectacle. August, the month when we made our ascent, is somewhat late; many plants were out of blossom. Those who really want to be successful should come up here in the first fortnight of July, and, above all, should forestall the arrival of the herds and flocks on these heights. Where a sheep has browsed one finds but poor remains. As yet spared by the grazing flocks, the stony screes on the top of Mont Ventoux are in July literally a bed of flowers. Memory calls up the lovely dew-bathed tufts of Androsace villosa, with white flowers and rosy centres; Viola cenisia, opening great blue corollas on the shattered heaps of limestone; Valeriana saliunca, with perfumed blossoms, but roots that smell like dung; Globularia cordifolia, forming close carpets of a crude green, starred with little blue heads; Alpine forget-me-not, blue as the sky above it; the iberis of Candolle, whose slender stalk bears a dense head of tiny white flowers and creeps down among the loose stones; Saxifraga oppositifolia and [[192]]S. muscoides, both making dark thick little cushions, the former with purple blossoms, the latter with white, washed with yellow. When the sun is hotter one sees a splendid butterfly flutter from one blossomed tuft to another, its white wings marked by four patches of vivid rose-carmine encircled with black. It is Parnassius apollo, the graceful dweller in Alpine solitudes, near the eternal snows. Its caterpillar lives on saxifrages. With the Apollo let us end this sketch of the joys which await the naturalist on the top of Mont Ventoux and return to the Ammophila hirsuta, crouching in great numbers under a sheltering stone, when the rain came up and surrounded us. [[193]]
XIV
THE EMIGRANTS
I have already told how on the top of Mont Ventoux, some 6000 feet above the sea, I had one of those pieces of entomological good luck, which would be fruitful indeed did they but occur often enough to allow of continuous study. Unhappily mine is a unique observation, and I despair of repeating it. Future observers must replace my probabilities by certainties. I can only found conjectures on it.
Under the shelter of a large flat stone I discovered some hundreds of Ammophila hirsuta, heaped in a mass almost as compact as a swarm of bees. As soon as the stone was lifted all the small people began to move about, but without any attempt to take wing. I moved whole handfuls, but not one seemed inclined to leave the heap. Common interests appeared to unite them indissolubly. Not one would go unless all went. With all possible care I examined the flat stone which sheltered them, as well as the soil and immediate neighbourhood, but could discover no explanation of this strange assemblage. Finding nothing better to do, I tried [[194]]to count them, and then came the clouds to end my observations and plunge us into that perplexing darkness I have already described. At the first drops of rain I hastened to put back the stone and replace the Ammophila people under shelter. I give myself a good mark, as I hope the reader also will, for having taken the precaution of not leaving the poor things, disturbed by my curiosity, exposed to the downpour.
[To face p. 194.
AMMOPHILA HIRSUTA ATTACKING A GRUB