Imágenes de páginas

our feet, we reached and reposed ourselves upon a narrow flat which is the last of three from the foot of the small mountain, and which, according to M. de Saussure, is but 150 fathoms below the level of the summit. Upon this platform I found a beautiful dead butterfly, the only appearance which, from the time I entered on the snow, I had seen of any animal. The pernicious effects of the thinness of the air were now evident on us all; a desire, almost irresistible, of sleep came on. My spirits had left me; sometimes indifferent as to the event, I wish

atmosphere began to affect my head with a dull and heavy pain. I also found, to my great surprise, an acute sensation of pain, very different from that of weariness, immediately above my knees. Having finished our repast, we pursued our journey, and soon arrived at a chasm which could not have existed many days, for it was not formed at the time of M. de Saussure's ascent. Misled by this last circumstance, for we concluded that, as he had seen no rents whatever from the time that he passed the place where he slept the second night, none were likely to be formed, we had left our lad-ed to lie down; at others, I blamder about a league behind; but as the chasm was far from wide, we passed it on the poles that we used for walking; an expedient which suggested to me that the length of our ladder might be easily increased by the addition of several poles laid parallel and fastened to its end; and that the hazard of finding our retreat cut off from the enlargement of the chasms might by this means be materially diminished. At this place I had an opportunity of measuring the height of the snow which had fallen during the preceding winter, and which was distinguished by its superior whiteness from that of the former year. I found it to be five feet. The snow of each particular year appeared as a separate stratum; that which was more than a twelvemonth old was perfect ice; while that of the last winter was fast approaching to a similar state. At length, after a difficult ascent, which lay among precipices, and during which we were often obliged to employ the hatchet in making a footing for

ed myself for the expedition; and, though just at the summit, had thoughts of turning back, without accomplishing my purpose. Of my guides many were in a worse situation; for, exhausted by excessive vomiting, they seemed to have lost all strength, both of mind and body. But shame at length came to our relief. I drank the last pint of water that was left, and found myself amazingly refreshed. Yet the pain in my knees had increased so much, that at the end of every 20 or 30 paces I was obliged to rest till its sharpness was abated. My lungs with difficulty performed their office, and my heart was affected with violent palpitation. At last, however, but with a sort of apathy which scarcely admitted the sense of joy, we reached the summit of the mountain; when six of my guides, and with them my servant, threw themselves on their faces, and were immediately asleep. I envied them their repose; but my anxiety to obtain a good observation for the latitude subdued my

wishes for indulgence. The time of my arrival was half an hour after ten; so that the hours which had elapsed from our departure from Chamouni were only 27, 10 of which we had passed in the hut. The summit of the hill is formed of snow, which spreads into a sort of plain which is much wider from E. to W. than from N. to S., and in its greatest width is perhaps 30 yards. The snow is every where hard, and in many places is covered with a sheet of ice. When the spectator begins to look round him from this elevated height, a confused impression of immensity is the first effect produced upon his mind; but the blue colour, deep almost to blackness, of the canopy above him soon arrests his attention. He next surveys the mountains; many of which, from the clearness of the air, are to his eye within a stone's throw from him; and even those of Lombardy (one of which appears of an altitude but little inferior to that of Mount Blanc) seem to approach his neighbourhood; while on the other side the vale of Chamouni glittering with the sunbeams is to the view directly below his feet, and affects his head with giddiness. On the other hand, all objects of which the distance is great, and the level low, are hid from his eye by the blue vapour which intervenes, and through which I could not discern the Lake of Geneva, though at the height of 15,700 English feet, which, according to M. de Saussure, was the level on which I stood: even the Mediterranean Sea must have been within the line of vision. The air was still; and the day so re

markably fine, that I could not discover in any part of the heavens the appearance of a single cloud. As the time of the sun passing the meridian now approached, I prepared to take my observation. I had with me an admirable Hadley's sextant, and an artificial horizon, and I corrected the mean refraction of the sun's rays. Thus I was enabled to ascertain with accuracy that the latitude of the summit of Mount Blanc is 45° 49′ 59′′ North.

I now proceeded to such other observations as the few instruments which I had brought permitted me to make. At twelve o'clock the mercury in the thermometer stood at 38° in the shade; at Chamouni, at the same hour, it stood when in the shade at 78°. I tried the effect of a burning glass on paper, and on a piece of wood, which I had brought with me for the purpose, and found (contrary, I believe, to the generally received opinion) that its power was much greater than in the lower regions of the air. Having continued two hours on the summit of the mountain, I began my descent at half an hour after twelve. I found that, short as my absence had been, many new rents were opened, and that several of those which I had passed in my ascent were become considerably wider. In less than six hours we arrived at the hut in which we had slept the evening before, and should have proceeded much further down the mountain had we not been afraid of passing the Glaciere de la Coté at the close of the day, when the snow, from the effect of the sun-beams, was extremely rotten. Our evening's


repast being finished, I was soon asleep; but in a few hours I was awakened with a tormenting pain in my face and eyes. My face was one continued blister, and my eyes I was unable to open; nor was I without apprehensions of losing my sight for ever, till my guides told me that if I had condescended to have taken their advice of wearing, as they did, a mask of black crape, the accident would not have befallen me, but that a few days would perfectly restore the use of my eyes. After I had bathed them with warm water for half an hour, I found to my great satisfaction that I could open them a little, on which I determined upon an instant departure, that I might cross the Glaciere de la Coté before the sun was sufficiently high for its beams to be strongly reflected from the snow. But unluckily the sun was already above the horizon; so that the pain of forcing open my eyes in the bright sunshine, in order to avoid the chasms, and other hazards of my way, rendered my return more irksome than my ascent. Fortunately one of the guides, soon after I had passed the glaciere, picked up in the snow a pair of green spectacles, which M. Bourrit had lost, and which gave me wonderful relief.

At eleven o'clock on Aug. 10, after an absence of 52 hours, of which 20 were passed in the hut, I returned again to the village of Chamouni. From the want of instruments (the scale of the barometers I had, being graduated no lower than 20 inches, which was not sufficiently extended) the observations I made were but few. Yet the effects which the air in

the heights I visited produced on the human body may not perhaps be considered as altogether uninteresting, nor will the proof I made of the power of the lens on the summit of Mount Blanc, if confirmed by future experiments, be regarded as of no account in the theories of light and heat. At any rate, the having determined the latitude of Mount Blanc may assist in some particulars the observations of such persons as shall visit it in future; and the knowledge which my journey has afforded, in addition to that which is furnished by M. de Saussure, may facilitate the ascent of those who, with proper instruments, may wish to make in that elevated level experiments in natural philosophy.

Notes of a Mineralogical Excursion to the Giant's Causeway. By the Rev. Dr. Grierson.

(From the same.)

I left Coleraine on the morning of Sept. 17, in company with a gentleman of that place, whose obligingness, intelligence, hospitality, and kindness, afforded me a most agreeable specimen of the Irish character; and proceeded to the Giant's Causeway. The day was charming; and it is not easy for me to express the gratification I felt, as we made our way through a fine and gently varied district, at the idea of having it in my power soon to contemplate in favourable circumstances one of the most stupendous and interesting natural phenomena that are any where to be seen. From Coleraine to the Causeway is eight

miles in a northerly direction, and I could observe no rock on our way but the trap formation. On crossing the river Bush at the village called Bushmills, the country begins gradually to rise, and we descry about two miles before us a ridge of considerable height, seeming to terminate quite abruptly on the other side. What we perceive is the land side of the precipice of the Giant's Causeway. It seems to have been a hill of basalt, with nearly perpendicular columnar concretions, cut in two, as it were, by a vertical section, and the half of the hill next the sea carried away. On getting in front of this precipice, which you do by a pass on the west side of it, a most stupendous scene presents itself. The precipice, extending for a mile or two along the shore, is in many places quite perpendicular, and often 350 and 400 feet high, consisting of pure columnar basalt, some of the columns 50 feet

in perpendicular height, straight and smooth as if polished with a chisel. In other parts the columns are smaller, inclined, or bent; and a less length of them strikes the eye. From the bottom of this precipice issues, with a gentle slope of about 1 in 30 towards the sea, an immense and surprising pavement, as it were, consisting of the upper ends of the fragments of vertical columns of basalt that have been left when the seaward half of the basaltic hill was carried off. The ends of these columns are in general 15 or 20 inches in diameter, some of them of three sides, some four, five, six, seven, eight, or even nine. Five and six sides seem to prevail most. From the bottom

of the precipice to the sea at low water along this pavement or causeway, which, from the artificial appearance it puts on, has, doubtless, in a rude age, given name to the place, is a length of 730 feet. It has been observed to proceed into the ocean as far as can be traced by the eye in a calm and clear day. To any person who has seen both this place and Staffa, the idea naturally enough suggests itself that they are parts of the same once continuous immense bed of columnar basalt. There are properly three pavements proceeding into the sea, distinguished by the names of the Great

Causeway, the Middle Causeway, and the West Causeway. These are three large gently sloping ridges of the ends of basaltic columns, with depressions between them, covered with large blocks or masses, that seem to have from time to time been detached, and rolled from the precipice. I had no opportunity of perceiving with what rocks the basalt of the Giant's Causeway is connected. I am told conchoidal white lime-stone meets it on both the east and west sides. There is in one place near the east side of the Great Causeway a green-stone vein eight or ten feet wide intersecting the basalt from north-west to south-east.

There was now pointed out to us by the guides a singular enough and curious phenomenon, and which is particularly interesting, as it has been thought by those who hold the igneous origin of basalt to be a confirmation of their doctrine. Nearly opposite to the West Causeway, and within about 80 feet of the top of the cliff, is


found to exist a quantity of slags and ashes, unquestionably the production of fire. On ascending to On ascending to this spot, which can be easily done, I found the slags and ashes deposited in a sort of bed about four feet thick, and running horizontally along the face of the basaltic precipice 20 or 30 feet. The ashes are in general observed to lie undermost, and the slags above them. They are covered with a considerahle quantity of earth and stones, which all consist of basalt, are of a large size, some of them three or four feet or more in diameter, and the ashes likewise rest on the same sort of materials. What struck me here was, that these ashes and slags are entirely unconnected with any rock or formation which seems to be in situ, or in its original position. They are, therefore, in my opinion, distinctly artificial, and nothing more than the remains of some large and powerful fire which had been kept burning for a long while on the top of this precipice, either for the purpose of a signal, or some other which we cannot now ascer

tain; and that, owing to the part

of the cliff on which the ashes were lying having given way and tumbled down, they have been thus buried beneath the ruins and there remain. This hypothesis may appear to some fanciful or extravagant, but I should have little hesitation in referring the truth of it to any unprejudiced person accustomed to investigations of this sort who will be at the trouble to scramble up and survey the spot. Nay, I think I could even trust the decision to a Huttonian himself! The mass of materials in which the slags and

ashes are found is clearly moved from its place, and has distinctly the appearance of a large slip of loose pieces of rock and soil that has been disengaged by means of frost or some other agent. It may have been effected by an earthquake: or the fire itself may have contributed to its own removal by the rents or cracks its heat made in the rock on which it stood. It is not a great many years since these ashes were noticed. John Corry, one of the most obliging and intelligent guides about the place, picked up some of them on the beach below, and naturally enough concluding that they came from the cliff above, he climbed up and found their repository. One gentleman, he informed us, who is well known to have paid much attention to the appearances at the Giant's Causeway, and who has written upon the subject, will not yet believe that the ashes are found in the place which I have described, but insists (obstinately enough, no doubt!) that honest John and his colleagues have put the ashes there on purpose to deceive the public! He cannot be prevailed upon to scramble up and look at the ashes himself, verifying, it would seem, the old proverb, which says, that there is no one blinder than he who will not see.

A considerable way from the repository of the ashes and slags, and to the east of the Great Causeway, is another curious appearance. Here, in the pure basalt, 70 or 80 feet from the top of the cliff, is a horizontal bed of wood coal eight feet thick. The coal to all appearance rests immediately on the basalt below, and the ends of perpendicular basaltic columns


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