remained there an hour to breakfast and to enable me to make the following observations: The Barometer stood at Thermometer in the shade Wet-bulb Thermometer Boiling point of water. In. 20,654 44° F. 4 140 196.7 I am not certain that this is perfectly correct, as it varied from 196° 4 to 1967, the bulb of the thermometer was not plunged into the water, but in the steam about an inch above the surface of the water. We began to mount the Peak on foot, by a very steep ascent over a surface covered with yellowish coloured pumice, between two embankments or currents of trachytic lava, which had separated in cooling from the general mass called Mal Pais, situated at Alta Vesta de Arriba 10,621 feet above the sea. It is not quite correct to call them currents; although in continuous lines, the lava was not in connected masses, but in large detached blocks of various sizes and forms, that had apparently undergone various degrees of rapid and slow cooling; the most common description was a trachy-dolerite, with more or less felspathic minerals; some were obsidian, or volcanic glass, of a jet-black colour, having internally a shining vitreous lustre, breaking with a conchoidal fracture, and translucent at the edges. It is worthy of remark, that when I broke some specimens from the lowest part of a mass of obsidian they contained crystals of felspar, but in the upper part of the same mass, very frequently I could not discover a single crystal, as if they had fallen down to the bottom, when the mass was liquid, by their own specific gravity. On breaking some of them, they exhibited cavities containing an incipient crystallization forming concentric laminæ of a lighter colour than the rest. In some places I picked up pieces which were slightly convoluted, containing small crystals of pyroxene and glassy felspar. Another singular circumstance is, that the pumice taken from the Cañadas of the Peak is heavier and contains more silica and alumina, and less potash and soda, than that on the sides and top of the Peak; the latter contained about the same quantity of silica and alumina as the trachy-dolerite. The following is the analysis made for me by the late Dr. Andrew Ure: It will be seen that all this pumice contains a smaller amount of silica than that from the Lipari Isles, which according to Klaproth contains 77.50 of silica and 17 50 of alumina. Some of the blocks of lava I examined higher up the Peak had more of a porphyritic than a trachytic character, as they contained blotches of crystals of a greenish and greyish-white colour, which I mistook for ordinary felspar; but I was informed on good authority that they were pyroxene, labradorite, and chrysolite, therefore the blocks may be more properly considered a species of basalt, though they had all the spongy and rough appearance of a trachyte. Occasionally there were detached blocks of phonolite, of a greyishblue colour, containing much felspar and mesotype; it made a smooth fracture, and had the peculiar metallic sound of that rock when struck with a hammer. After a very fatiguing but not difficult ascent, which took us an hour, including the time occupied in examining the lavas, we arrived at a part of the Peak called La Estancia de los Ingleses de Abaxo (the lower halting place of the English), which is 9,930 feet above the level of the sea. The pumice here forms a tolerably level surface of a few hundred feet square; towards the N.N.E. side of it are some large scattered blocks of obsidian, under the lee of one of them we piled up some pieces of lava to form a slight shelter from the wind, which was extremely cold, and blew such a gale that we were frequently obliged to hold on to the rocks to avoid being blown away, and which for some time made all our efforts useless to light a fire of mountain broom. At sunset it suddenly abated, and two hours after there was a calm, occasionally interrupted by violent gusts of wind, which rushed along with a noise like distant thunder in a mountainous country. After partaking of a supper of hot coffee, bread, and roasted potatoes, we made a trench in the pumice, in which I placed my guide and muleteer, and then covered them up to the neck with light pumice-dust, over which I put my cloak. This simple plan so effectually protected them from the bitter cold, that I soon found they had forgotten all the fatigues in a sound slumber. As I wished to note the barometer and thermometer every hour, and had agreed with some friends at Port Orotava and the Villa, to observe them at the same time during part of the twentyfour hours, I was unable to take the rest which I so much required. The strange and interesting scene around me caused a feeling which partook in some degree of pleasure and pain; not having anyone to whom I could express my feelings, produced a painful void. The peculiar wildness of the scene was in some degree enlivened by the splendour of the starry vault above, which was so extremely blue, that if it had been seen in a picture, it might have been thought unnatural. From the clearness of the atmosphere, the light given by the stars and planets was sufficient to enable me to write my observations, and Venus left a faint glimmering streak of light on a wreath of snow close to our resting-place; and when the moon arose, I could distinctly see the degrees on my instruments. A still stronger proof of the extreme clearness of the atmosphere was, that I observed the moon to be indented like a saw, between the light and obscured part, which I supposed was caused by the projection of the illuminated tops of the mountains upon the part which was deprived of the sun's light. Soon after dark a broad pyramidal body of light appeared, like the glow on the sky caused by a distant conflagration; this was the zodiacal light; where there were openings in the clouds below, the brightness continued close down to the horizon, with as deep a tone as that of the zenith. It was much broader below, occupying a space equal to what I considered to be nearly 15° in breadth. Orion was so clear, that if I had had a telescope of even moderate power, no doubt I might have seen the whole of his sword. Another phenomenon I observed may be worth mentioning. Soon after the sun went down, the wind became much louder and had an acuter sound, although the force was very considerably less than it was before. It has been observed, from the earliest antiquity, that the air becomes more sonorous at night than in the day, but I am not aware that the cause of it has been well ascertained. The general opinion is, I believe, that the air, becoming colder, is therefore denser, and more susceptible of conveying the sonorous waves. Our navigators to the North Pole have frequently mentioned the surprising distance from which they were enabled to hear sound during an Arctic winter. My observations of the intensity of sound at different states of the atmosphere were not confined to the Peak. At the town of Orotava, situated about two miles from the sea, the noise of the waves in the morning occasionally had a grave, low tone; at the same time, the air appeared to be particularly dry, and distant objects were very indistinct. Towards the middle of the day, or the beginning of the afternoon, and when the difference between the dry and wet bulb thermometer was less than usual, the island of Palma, nearly sixty miles distant, could be distinctly seen, and the mountains that surround the valley of Orotava were brought apparently so close, that the vegetation upon them could be observed; at the same time, the sound of the sea invariably passed from a grave to an acute sound. The natives prognosticate rain when they observe this particular clearness of the atmosphere, and generally I have found them correct. I have made the same remark during my long residence in Chili, where the distant Andes are apparently only a few miles off shortly before rain, and the noise of the waves of the sea, dashing on the rocky coast, assumes a different tone. From frequent observations that I have made, I am inclined to attribute the intensity of sound at night to a certain increase of moisture, and to an equability of temperature in the different strata of the atmosphere. The increased intensity of sound when I was on the Peak during the night could not have been caused by an increased density of the atmosphere, because, instead of becoming colder, it was four or five degrees warmer when the sound of the wind became more sonorous. The instruments were observed every hour, and the boilingpoint of water was noted four times, giving an average of 193° 64; the barometer, an average pressure of 2° 329. This boiling-point does not exactly agree with the experiments of General Roy, who considered that the boiling-point of water varied 0.88 of a degree for every half-inch of a variation of the barometer At the Villa de Orotava, at an elevation of 1,141 feet, I found the average boiling-point to be 209° 178,- the thermometer was not in the water, but close above it. In the subjoined table I merely give the result of my observations at such times as there were notable differences. The difference of radiation was most astonishing: as night approached it fell 80° in an hour; at midnight it was negative, that is, the shaded thermometer was 9° higher than the exposed one. At first I thought it must be caused by local position, but I removed the thermometers three times, and found the results similar. I was surprised to find that, at the moment of sunrise, it was still negative, the shaded thermometer standing 4° higher than the other. At Alta Vista de Arriba, one hour and a half after sunrise, the black-bulb thermometer rose to 98°, and later to 126°, The following table is the result of my observations made at La Estancia de los Ingleses, 9,930 feet above the level of the sea: About an hour before sunrise I awoke my sleepy men, but my guide (who had never ascended to the top of the Peak) was seized with an affection like sea-sickness, and a violent pain in the head, no doubt caused by the rarity of the air, therefore I was obliged to leave him at the Estancia to await my return. VOL. III. In an hour we reached that part of the Peak directly above Alta Vista de Arriba, called Mal Pais (bad country), 10,730 feet above the sea. The part we arrived at was well named Mal Pais, as it was formed of immense masses of trachytic lava, thrown about in all imaginable shapes and directions, interspersed with large blocks of obsidian, some of which were like enormous bombshells; one or two small ones that I broke were hollow in the centre; the internal cavity was lined with thin filaments, similar to those found in flint nodules; the edges of some of the masses of obsidian were often as sharp as those of broken wine-bottles. The blocks of lava were sometimes wide apart, and sometimes had mere slits between them, but always wide enough to swallow up a pencil if one were dropped in. Some of the lavas looked as if they had run down the Peak in a half-fluid state, and had broken into detached masses in cooling. We had made our ascent up to this point by the lights of the spangled vault above, but it was impossible to proceed any further until daylight. We had not long to wait; in a few minutes a long and bright streak of light orange-colour began to tinge the eastern part of the fleecy clouds below; it then deepened into a rose-colour, which was reflected on the cone of the Peak just above us, and then followed such a magnificent blending of colours as to defy description, and the day-break rapidly chased away the darkness in the plain below. The cold was most penetrating; the thermometer stood at 21°, which was 13° below what it had stood at, at any time during the night, only 800 feet below. We again resumed our ascent, which over these rough masses was difficult and painful, as we were obliged to jump from block to block, aided by a long staff shod with steel, and occasionally to climb over some with the hands and feet. The greatest annoyance we experienced was from thick masses of snow between the blocks of lava, which had frozen hard, forming a surface like glass, thus making it extremely difficult to cross, particularly as I was unprovided with proper shoes. The thermometer soon rose to 34°; this sudden rise of temperature, combined with the great exertion of climbing, made me feel my overcoat oppressive, and I was glad to leave it, till my return, under a high block of obsidian. After some fatigue, we reached a spot called the Cueva de Nieve (the cave of snow), which is 11,098 feet above the level of the sea. At 7 A.M. the thermometer stood here at 42° 75, the barometer at 19° 912, and water boiled at 1922-78. This singular cave is always filled with ice and water; the entrance is merely a hole in the trachytic lava, about 40 inches square, and from 18 to 20 feet perpendicular depth; as I was not provided with a ladder, my man let me down by fastening a rope round my waist. I found the floor immediately below the |