Consolations in Travel; or, the Last Days of a Philosopher

by Sir Humphry Davy

we saw the white temples glittering in the sunshine. The blue Tyrrhene sea filled up the outline of this scene, which, though so beautiful, was not calm; there was a heavy breeze which blew full from the southwest; it was literally a zephyr, and its freshness and strength in the middle of the day were peculiarly balmy and delightful; it seemed a breath stolen by the spring from the summer. I never saw a deeper, brighter azure than that of the waves which rolled towards the shore, and which was rendered more striking by the pure whiteness of their foam. The agitation of nature seemed to be one of breathing and awakening life; the noise made by the waving of the branches of the pine above our heads and by the rattling of its cones was overpowered by the music of a multitude of birds which sung everywhere in the trees that surrounded us, and the cooing of the turtle-doves was heard even more distinctly than the murmuring of the waves or the whistling of the winds, so that in the strife of nature the voice of love was predominant. With our hearts touched by this extraordinary scene we descended to the ruins, and having taken at a farmhouse a person who acted as guide or cicerone, we began to examine those wonderful remains which have outlived even the name of the people by whom they were raised, and which continue almost perfect whilst a Roman and a Saracen city since raised have been destroyed. We had been walking for half an hour round the temples in the sunshine when our guide represented to us the danger that there was of suffering from the effects of malaria, for which, as is well known, this place is notorious, and advised us to retire into the interior of the temple of Neptune. We followed

his advice, and my companions began to employ themselves in measuring the circumference of one of the Doric columns, when they suddenly called my attention to a stranger who was sitting on a camp-stool behind it. The appearance of any person in this place at this time was sufficiently remarkable, but the man who was before us from his dress and appearance would have been remarkable anywhere. He was employed in writing in a memorandum book when we first saw him, but he immediately rose and saluted us by bending the head slightly though gracefully; and this enabled me to see distinctly his person and dress. He was rather above the middle stature, slender, but with well-turned limbs; his countenance was remarkably intelligent, his eye hazel but full and strong, his front was smooth and unwrinkled, and but for some grey hairs, which appeared silvering his brown and curly locks, he might have been supposed to have hardly reached the middle age; his nose was aquiline, the expression of the lower part of his countenance remarkably sweet, and when he spoke to our guide, which he did with uncommon fluency in the Neapolitan dialect, I thought I had never heard a more agreeable voice, sonorous yet gentle and silver-sounded. His dress was very peculiar, almost like that of an ecclesiastic, but coarse and light; and there was a large soiled white hat on the ground beside him, on which was fastened a pilgrim’s cockle shell, and there was suspended round his neck a long antique blue enamelled phial, like those found in the Greek tombs, and it was attached to a rosary of coarse beads. He took up his hat, and appeared to be retiring to another part of the building, when I apologised for

the interruption we had given to his studies, begged him to resume them, and assured him that our stay in the building would be only momentary, for I saw that there was a cloud over the sun, the brightness of which was the cause of our retiring. I spoke in Italian; he replied in English, observing that he supposed the fear of contracting the malaria fever had induced us to seek the shelter of the shade: but it is too early in the season to have much reasonable fear of this insidious enemy; yet, he added, this bottle which you may have observed here at my breast, I carry about with me, as a supposed preventive of the effects of malaria, and as far as my experience, a very limited one, however, has gone, it is effectual. I ventured to ask him what the bottle might contain, as such a benefit ought to be made known to the world. He replied, “It is a mixture which slowly produces the substance called by chemists chlorine, which is well known to be generally destructive to contagious matters; and a friend of mine who has lived for many years in Italy, and who has made a number of experiments with it, by exposing himself to the danger of fever in the worst seasons and in the worst places, believes that it is a secure preventive. I am not convinced of this; but it can do no harm; and in waiting for more evidence of its utility, I employ it without putting the least confidence in its power; nor do I expose myself to the same danger as my friend has done for the sake of an experiment.” I said, “I believe several scientific persons—Brocchi amongst others—have doubted the existence of any specific matter in the atmosphere producing intermittent fevers in marshy countries and hot climates; and have been more disposed

to attribute the disease to physical causes, dependent upon the great differences of temperature between day and night and to the refrigerating effects of the dense fogs common in such situations in the evening and morning; and, on this hypothesis, they have recommended warm woollen clothing and fires at night as the best preventives against these destructive diseases, so fatal to the peasants who remain in the summer and autumn in the neighbourhood of the maremme of Rome, Tuscany, or Naples.” The stranger said, “I am acquainted with the opinions of the gentlemen, and they undoubtedly have weight; but that a specific matter of contagion has not been detected by chemical means in the atmosphere of marshes does not prove its non-existence. We know so little of those agents that affect the human constitution, that it is of no use to reason on this subject. There can be no doubt that the line of malaria above the Pontine marshes is marked by a dense fog morning and evening, and most of the old Roman towns were placed upon eminences out of the reach of this fog. I have myself experienced a peculiar effect upon the organs of smell in the neighbourhood of marshes in the evening after a very hot day; and the instances in which people have been seized with intermittents by a single exposure in a place infested by malaria in the season of fevers gives, I think, a strong support to something like a poisonous material existing in the atmosphere in such spots; but I merely offer doubts. I hope the progress of physiology and of chemistry will at no very distant time solve this important problem.” Ambrosio now came forward, and bowing to the stranger, said he took the liberty, as he saw from his familiarity with the

cicerone that he was well acquainted with Pæstum, of asking him whether the masses of travertine, of which the Cyclopean walls and the temples were formed, were really produced by aqueous deposition from the River Silaro, as he had often heard reported. The stranger replied, “that they were certainly produced by deposition from water; and such deposits are made by the Silaro. But I rather believe,” he said, “that a lake in the immediate neighbourhood of the city furnished the quarry from which these stones were excavated; and, in half an hour, if you like, after you have finished your examinations of the temples with your guide, I will accompany you to the spot from which it is evident that large masses of the travertine, marmor tiburtinum, or calcareous tufa, have been raised.” We thanked him for his attention, accepted his invitation, took the usual walk round the temples, and returned to our new acquaintance, who led the way through the gate of the city to the banks of a pool or lake a short distance off. We walked to the borders on a mass of calcareous tufa, and we saw that this substance had even encrusted the reeds on the shore. There was something peculiarly melancholy in the character of this water; all the herbs around it were grey, as if encrusted with marble; a few buffaloes were slaking their thirst in it, which ran wildly away on our approach, and appeared to retire into a rocky excavation or quarry at the end of the lake; there were a number of birds, which, on examination, I found were sea swallows, flitting on the surface and busily employed with the libella or dragon-fly in destroying the myriads of gnats which rose from the bottom and were beginning to be very troublesome by their bites to us. “There,”

said the stranger, “is what I believe to be the source of those large and durable stones which you see in the plain before you. This water rapidly deposits calcareous matter, and even if you throw a stick into it, a few hours is sufficient to give it a coating of this substance. Whichever way you turn your eyes you see masses of this recently-produced marble, the consequence of the overflowing of the lake during the winter floods, and in that large excavation where you saw the buffaloes disappear you may observe that immense masses have been removed, as if by the hand of art and in remote times. The marble that remains in the quarry is of the same texture and character as that which you see in the ruins of Pæstum, and I think it is scarcely possible to doubt that the builders of those extraordinary structures derived a part of their materials from this spot.” Ambrosio gave his assent to this opinion of the stranger; and I took the liberty of asking him as to the quantity of calcareous matter contained in solution in the lake, saying that it appeared to me, for so rapid and considerable an effect of deposition, there must be an unusual quantity of solid matter dissolved by the water or some peculiar circumstance of solution. The stranger replied, “This water is like many, I may say most of the sources which rise at the foot of the Apennines: it holds carbonic acid in solution which has dissolved a portion of the calcareous matter of the rock through which it has passed. This carbonic acid is dissipated in the atmosphere, and the marble, slowly thrown down, assumes a crystalline form and produces coherent stones. The lake before us is not particularly rich in the quantity of calcareous matter that it contains, for, as I have found by experience,

a pint of it does not afford more than five or six grains; but the quantity of fluid and the length of time are sufficient to account for the immense quantities of tufa and rock which in the course of ages have accumulated in this situation.” Onuphrio’s curiosity was excited by this statement of the stranger, and he said, “May I take the liberty of asking if you have any idea as to the cause of the large quantity of carbonic acid which you have been so good as to inform us exists in most of the waters in this country?” The stranger replied, “I certainly have formed an opinion on this subject, which I willingly state to you. It can, I think, be scarcely doubted that there is a source of volcanic fire at no great distance from the surface in the whole of southern Italy; and, this fire acting upon the calcareous rocks of which the Apennines are composed, must constantly detach from them carbonic acid, which rising to the sources of the springs, deposited from the waters of the atmosphere, must give them their impregnation and enable them to dissolve calcareous matter. I need not dwell upon Etna, Vesuvius, or the Lipari Islands to prove that volcanic fires are still in existence; and there can be no doubt that in earlier periods almost the whole of Italy was ravaged by them; oven Rome itself, the eternal city, rests upon the craters of extinct volcanoes; and I imagine that the traditional and fabulous record of the destruction made by the conflagration of Phæton in the chariot of the sun and his falling into the Po had reference to a great and tremendous igneous volcanic eruption, which extended over Italy and ceased only near the Po at the foot of the Alps. Be this as it may, the sources of carbonic acid are numerous, not merely in the Neapolitan,

but likewise in the Roman and Tuscan states. The most magnificent waterfall in Europe, that of the Velino, near Terni, is partly fed by a stream containing calcareous matter dissolved by carbonic acid, and it deposits marble, which crystallises even in the midst of its thundering descent and foam in the bed in which it falls. The Anio or Teverone, which almost approaches in beauty to the Velino in the number and variety of its falls and cascatelle, is likewise a calcareous water; and there is still a more remarkable one which empties itself into this river below Tivoli, and which you have probably seen in your excursions in the campagna of Rome, called the lacus Albula or the lake of the Solfatara.” Ambrosio said, “We remember it well, we saw it this very spring; we were carried there to examine some ancient Roman baths, and we were struck by the blue milkiness of the water, by the magnitude of the source, and by the disagreeable smell of sulphuretted hydrogen which everywhere surrounded the lake.” The stranger said, “When you return to Latium I advise you to pay another visit to a spot which is interesting from a number of causes, some of which I will take the liberty of mentioning to you. You have only seen one lake, that where the ancient Romans erected their baths, but there is another a few yards above it, surrounded by very high rushes, and almost hidden by them from the sight. This lake sends down a considerable stream of tepid water to the larger lake, but this water is less strongly impregnated with carbonic acid; the largest lake is actually a saturated solution of this gas, which escapes from it in such quantities in some parts of its surface that it has the appearance of being actually in ebullition.

I have found by experiment that the water taken from the most tranquil part of the lake, even after being agitated and exposed to the air, contained in solution more than its own volume of carbonic acid gas with a very small quantity of sulphuretted hydrogen, to the presence of which, I conclude, its ancient use in curing cutaneous disorders may be referred. Its temperature, I ascertained, was in the winter in the warmest parts above 80° of Fahrenheit, and it appears to be pretty constant, for I have found it differ a few degrees only, in the ascending source, in January, March, May, and the beginning of June; it is therefore supplied with heat from a subterraneous source, being nearly twenty degrees above the mean temperature of the atmosphere. Kircher has detailed in his “Mundus Subterraneus” various wonders respecting this lake, most of which are unfounded, such as that it is unfathomable, that it has at the bottom the heat of boiling water, and that floating islands rise from the gulf which emits it. It must certainly be very difficult, or even impossible, to fathom a source which rises with so much violence from a subterraneous excavation, and, at a time when chemistry had made small progress, it was easy to mistake the disengagement of carbonic acid for an actual ebullition. The floating islands are real, but neither the Jesuit nor any of the writers who have since described this lake had a correct idea of their origin, which is exceedingly curious. The high temperature of this water, and the quantity of carbonic acid that it contains, render it peculiarly fitted to afford a pabulum or nourishment to vegetable life. The banks of travertine are everywhere covered with reeds, lichens, confervæ, and various

kinds of aquatic vegetables, and, at the same time that the process of vegetable life is going on, the crystallisations of the calcareous matter, which is everywhere deposited in consequence of the escape of carbonic acid, likewise proceed, giving a constant milkiness to what, from its tint, would otherwise be a blue fluid. So rapid is the vegetation, owing to the decomposition of the carbonic acid, that, even in winter, masses of confervæ and lichens, mixed with deposited travertine, are constantly detached by the currents of water from the bank and float down the stream, which being a considerable river is never without many of these small islands on its surface; they are sometimes only a few inches in size, and composed merely of dark-green confervæ or purple or yellow lichens, but they are sometimes even of some feet in diameter, and contain seeds and various species of common water-plants, which are usually more or less encrusted with marble. There is, I believe, no place in the world where there is a more striking example of the opposition or contrast of the laws of animate and inanimate Nature, of the forces of inorganic chemical affinity and those of the powers of life. Vegetables in such a temperature, and everywhere surrounded by food, are produced with a wonderful rapidity, but the crystallisations are formed with equal quickness, and they are no sooner produced than they are destroyed together. Notwithstanding the sulphureous exhalations from the lake, the quantity of vegetable matter generated there and its heat make it the resort of an infinite variety of insect tribes, and even in the coldest days in winter numbers of flies may be observed on the vegetables surrounding its banks or on its floating island’s, and a