Part 3 (1/2)
The length is fixed at fifteen feet, because I have found this length extremely efficient in similar experiments.
[Ill.u.s.tration: Fig. 3, 4. Boats' sails inverted by Atmospheric Refraction.]
[Sidenote: ATMOSPHERIC REFRACTION. 1857.]
On returning to the pier at Villeneuve, a peculiar flickering motion was manifest upon the surface of the distant portions of the lake, and I soon noticed that the coast line was inverted by atmospheric refraction.
It required a long distance to produce the effect: no trace of it was seen about the Castle of Chillon, but at Vevey and beyond it, the whole coast was clearly inverted; and the houses on the margin of the lake were also imaged to a certain height. Two boats at a considerable distance presented the appearance sketched in Figs. 3 and 4; the hull of each, except a small portion at the end, was invisible, but the sails seemed lifted up high in the air, with their inverted images below; as the boats drew nearer the hulls appeared inverted, the apparent height of the vessel above the surface of the lake being thereby nearly doubled, while the sails and higher objects, in these cases, were almost completely cut away. When viewed through a telescope the sensible horizon of the lake presented a billowy tumultuous appearance, fragments being incessantly detached from it and suspended in the air.
[Sidenote: MIRAGE. 1857.]
The explanation of this effect is the same as that of the mirage of the desert, which may be found in almost any book on physics, and which so tantalized the French soldiers in Egypt. They often mistook this aerial inversion for the reflection from a lake, and on trial found hot and sterile sand at the place where they expected refres.h.i.+ng waters. The effect was shown by Monge, one of the learned men who accompanied the expedition, to be due to the total reflection of very oblique rays at the upper surface of the layer of rarefied air which was nearest to the heated earth. A sandy plain, in the early part of the day, is peculiarly favourable for the production of such effects; and on the extensive flat strand which stretches between Mont St. Michel and the coast adjacent to Avranches in Normandy, I have noticed Mont Tombeline reflected as if gla.s.s instead of sand surrounded it and formed its mirror.
[Sidenote: CHAMOUNI AND THE MONTANVERT. 1857.]
CHAMOUNI AND THE MONTANVERT.
(5.)
On the evening of the 12th of July I reached Chamouni; the weather was not quite clear, but it was promising; white c.u.muli had floated round Mont Blanc during the day, but these diminished more and more, and the light of the setting sun was of that lingering rosy hue which bodes good weather. Two parallel beams of a purple tinge were drawn by the shadows of the adjacent peaks, straight across the Glacier des Bossons, and the Glacier des Pelerins was also steeped for a time in the same purple light. Once when the surrounding red illumination was strong, the shadows of the Grands Mulets falling upon the adjacent snow appeared of a vivid green.
This green belonged to the cla.s.s of _subjective_ colours, or colours produced by contrast, about which a volume might be written. The eye received the impression of green, but the colour was not external to the eye. Place a red wafer on white paper, and look at it intently, it will be surrounded in a little time by a green fringe: move the wafer bodily away, and the entire s.p.a.ce which it occupied upon the paper will appear green. A body may have its proper colour entirely masked in this way.
Let a red wafer be attached to a piece of red gla.s.s, and from a moderately illuminated position let the sky be regarded through the gla.s.s; the wafer will appear of a vivid green. If a strong beam of light be sent through a red gla.s.s and caused to fall upon a screen, which at the same time is moderately illuminated by a separate source of white light, an opaque body placed in the path of the beam will cast a green shadow upon the screen which may be seen by several hundred persons at once. If a blue gla.s.s be used, the shadow will be yellow, which is the complementary colour to blue.
[Sidenote: COLOURED SHADOWS. 1857.]
When we suddenly pa.s.s from open sunlight to a moderately illuminated room, it appears dark at first, but after a little time the eye regains the power of seeing objects distinctly. Thus one effect of light upon the eye is to render it less sensitive, and light of any particular colour falling upon the eye blunts its appreciation of that colour. Let us apply this to the shadow upon the screen. This shadow is moderately illuminated by a jet of white light; but the s.p.a.ce surrounding it is red, the effect of which upon the eye is to blind it in some degree to the perception of red. Hence, when the feeble white light of the shadow reaches the eye, the red component of this light is, as it were, abstracted from it, and the eye sees the residual colour, which is green. A similar explanation applies to the shadows of the Grands Mulets.
On the 13th of July I was joined by my friend Mr. Thomas Hirst, and on the 14th we examined together the end of the Mer de Glace. In former times the whole volume of the Arveiron escaped from beneath the ice at the end of the glacier, forming a fine arch at its place of issue. This year a fraction only of the water thus found egress; the greater portion of it escaping laterally from the glacier at the summit of the rocks called _Les Mottets_, down which it tumbled in a fine cascade. The vault at the end of the glacier was nevertheless respectable, and rather tempting to a traveller in search of information regarding the structure of the ice. Perhaps, however, Nature meant to give me a friendly warning at the outset, for, while speculating as to the wisdom of entering the cavern, it suddenly gave way, and, with a crash which rivalled thunder, the roof strewed itself in ruins upon the floor.
[Sidenote: SUNRISE AT CHAMOUNI. 1857.]
Many years ago I had read with delight Coleridge's poem ent.i.tled 'Sunrise in the Valley of Chamouni,' and to witness in all perfection the scene described by the poet, I waited at Chamouni a day longer than was otherwise necessary. On the morning of Wednesday, the 15th of July, I rose before the sun; Mont Blanc and his wondrous staff of Aiguilles were without a cloud; eastward the sky was of a pale orange which gradually shaded off to a kind of rosy violet, and this again blended by imperceptible degrees with the deep zenithal blue. The morning star was still s.h.i.+ning to the right, and the moon also turned a pale face towards the rising day. The valley was full of music; from the adjacent woods issued a gush of song, while the sound of the Arve formed a suitable ba.s.s to the shriller melody of the birds. The mountain rose for a time cold and grand, with no apparent stain upon his snows. Suddenly the sunbeams struck his crown and converted it into a boss of gold. For some time it remained the only gilded summit in view, holding communion with the dawn while all the others waited in silence. These, in the order of their heights, came afterwards, relaxing, as the sunbeams struck each in succession, into a blush and smile.
[Sidenote: GLACIER DES BOIS. 1857.]
On the same day we had our luggage transported to the Montanvert, while we clambered along the lateral moraine of the glacier to the Chapeau.
The rocks alongside the glacier were beautifully scratched and polished, and I paid particular attention to them, for the purpose of furnis.h.i.+ng myself with a key to ancient glacier action. The scene to my right was one of the most wonderful I had ever witnessed. Along the entire slope of the Glacier des Bois, the ice was cleft and riven into the most striking and fantastic forms. It had not yet suffered much from the wasting influence of the summer weather, but its towers and minarets sprang from the general ma.s.s with clean chiselled outlines. Some stood erect, others leaned, while the white debris, strewn here and there over the glacier, showed where the wintry edifices had fallen, breaking themselves to pieces, and grinding the ma.s.ses on which they fell to powder. Some of them gave way during our inspection of the place, and shook the valley with the reverberated noise of their fall. I endeavoured to get near them, but failed; the chasms at the margin of the glacier were too dangerous, and the stones resting upon the heights too loosely poised to render persistence in the attempt excusable.
We subsequently crossed the glacier to the Montanvert, and I formally took up my position there. The rooms of the hotel were separated from each other by wooden part.i.tions merely, and thus the noise of early risers in one room was plainly heard in the next. For the sake of quiet, therefore, I had my bed placed in the _chateau_ next door,--a little octagonal building erected by some kind and sentimental Frenchman, and dedicated ”_a la Nature_.” My host at first demurred, thinking the place not ”_propre_,” but I insisted, and he acquiesced. True the stone floor was dark with moisture, and on the walls a glistening was here and there observable, which suggested rheumatism, and other penalties, but I had had no experience of rheumatism, and trusted to the strength which mountain air and exercise were sure to give me, for power to resist its attacks. Moreover, to dispel some of the humidity, it was agreed that a large pine fire should be made there on necessary occasions.
[Sidenote: QUARTERS AT THE MONTANVERT. 1857.]
Though singularly favoured on the whole, still our residence at the Montanvert was sufficiently long to give us specimens of all kinds of weather; and thus my chateau derived an interest from the mutations of external nature. Sometimes no breath disturbed the perfect serenity of the night, and the moon, set in a black-blue sky, turned a face of almost supernatural brightness to the mountains, while in her absence the thick-strewn stars alone flashed and twinkled through the transparent air. Sometimes dull dank fog choked the valley, and heavy rain plashed upon the stones outside. On two or three occasions we were favoured by a thunderstorm, every peal of which broke into a hundred echoes, while the seams of lightning which ran through the heavens produced a wonderful intermittence of gloom and glare. And as I sat within, musing on the experiences of the day, with my pine logs crackling, and the ruddy fire-light gleaming over the walls, and lending animation to the visages sketched upon them with charcoal by the guides, I felt that my position was in every way worthy of a student of nature.