the funnel of the boiling spring, one-third of its diameter, and surrounded by perpendicular walls, goes down to a depth of 75 feet. The temperature of the water which constantly fills the basin is 180°. At very regular intervals of one hour and 20 or 30 minutes the thunder below proclaims the commencement of the eruption. The jets of water, of 9 feet in thickness, of which about three large ones follow one another, attain a height of 100 and sometimes 150 feet. The temperature of the water ascending in the funnel has been found to be 260°.6 at a depth of 72 feet a little while before the eruption, during the eruption 255°.5, and immediately after it 251°.6; at the surface of the basin it is only 183-185°. The Strokkr, which is also situated at the base of the Bjarnafell, has a smaller mass of water than the Geysir. The sinter margin of its basin is only a few inches in height and breadth. The eruptions are more frequent than in the Geysir, but do not announce themselves by subterranean thunder. In the Strokkr the temperature during the eruption is 235°-239° at a depth of 42 feet, and almost 212° at the surface. The eruptions of the intermittent boiling springs, and the slight changes in the type of the phenomena are perfectly independent of the eruptions of Hecla, and were by no means disturbed by the latter in the years 1845 and 1846.50 With his peculiar acuteness in observation and discussion, Bunsen has refuted the earlier hypotheses regarding the periodicity of the Geysir eruptions (subterranean cauldrons, which, as steam-boilers, are filled sometimes with vapours and sometimes with water). According to him the eruptions are caused by a portion of the column of water which

50 Sartorius von Waltershausen, Physisch-geographische Skizze von Island, mit besonderer Rücksicht auf vulkanische Erscheinungen, 1847, s. 128-132; Bunsen and Descloiseaux, in the Comptes rendus des Séances de l'Acad. des Sciences, t. xxiii, 1846, p. 935; Bunsen, in the Annalen der Chemie und Pharmacie, Bd. lxii, 1847, s. 27-45. Lottin and Robert had already found that the temperature of the jet of water in the Geysir diminishes from below upwards. Amongst the forty silicious bubbling springs, which are situated in the vicinity of the Great Geysir and Strokkr, one bears the name of the Little Geysir. Its jet of water only rises 20 or 30 feet. The term boiling springs (Kochbrunnen) is derived from the word Geysir, which is connected with the Icelandic giosa (to boil). On the high land of Thibet also, according to the report of Esoma de Körös, there is, near the Alpine lake Mapham a Geysir, which rises to the height of 12 feet.

has acquired a high temperature at a lower point under great pressure of accumulated vapours, being forced upwards, and thus coming under a pressure which does not correspond with its temperature. In this way "the Geysirs are natural collectors of steam power."

Of the hot springs a few approach nearly to absolute purity; others contain solutions of 8-12 parts of solid or gaseous matters. Among the former are the baths of Luxeueil, Pfeffer, and Gastein, the efficacy of which may appear so mysterious on account of their purity. As all springs are fed principally by meteoric water, they contain nitrogen, as Boussingault has proved in the very pure springs flowing from the granite in las Trincheras de Portocabello, and Bunsen53 in the Cornelius spring at Aix and in the Geysir of Iceland. The organic matter dissolved in many springs also contains nitrogen, and is even sometimes bituminous. Until it was known from the experiments of Gay-Lussac and myself that rain and snow-water contain more oxygen than the atmosphere (the former 10, and the latter at least 8 per cent. more) it appeared very remarkable that a gaseous mixture, rich in oxygen, could be evolved from the springs of Nocera in the Apennines. The analyses made by Gay-Lussac during our stay at this mountain spring showed that it only contained as much oxygen as might have been furnished to it by atmospheric moisture.54 If we be astonished at the

51 Trommsdorf finds in the springs of Gastein only 0.303 of solid constituents in 1000 parts; Löwig, 0.291 in Pfeffer; and Longchamp only 0.236 in Luxeuil; on the other hand, 0.478 were found in 1000 parts of common well water in Berne; 5.459 in the Carlsbad bubbling spring; and even 7.454 in Wiesbaden (Studer, Physikal. Geographie und Geologie, ed. 2, 1847, cap. i, s. 92).

52 The hot springs which gush from the granite of the Cordillera of the coast (of Venezuela), are nearly pure; they only contain a small quantity of silica in solution, and hydrosulphuric acid gas, mixed with a little nitrogen. Their composition is identical with that which would result from the action of water upon sulphuret of silicium" (Annales de Chimie et de Physique, t. lii, 1833, p. 189). Upon the great quantity of nitrogen which is contained in the hot spring of Orense (154°.4), see Maria Rubio, Tratado de las Fuentes Minerales de España, 1853, p. 331.

53 Sartorius von Waltershausen, Skizze von Island, s. 125.

54 The distinguished chemist Morechini of Rome, had stated the oxygen contained in the spring of Nocera (situated 2240 feet above the sea) to be 0.40; Gay-Lussac (26 September, 1805) found the exact

silicious deposits as a constructive material of which nature, as it were, artificially composes the apparatus of Geysirs, we must remember that silicic acid is also diffused in many cold springs which contain a very small portion of carbonic acid.

Acid springs and jets of carbonic acid gas, which were long ascribed to deposits of coal and lignite, appear rather to belong entirely to the processes of deep volcanic activity :an activity which is universally disseminated, and therefore does not exert itself merely in those places where volcanic rocks testify to the existence of ancient local fiery eruptions. In extinguished volcanoes jets of carbonic acid certainly remain longest after the Plutonic catastrophes; they follow the stage of Solfatara activity; but nevertheless waters impregnated with carbonic acid, and of the most various temperatures, burst forth from granite, gneiss, and old and new floetz mountains. Acid springs become impregnated with alkaline carbonates, and especially with carbonate of soda, wherever water impregnated with carbonic acid acts upon rocks containing alkaline silicates.55 In the north of Germany many of the carbonic acid springs and gaseous jets are particularly remarkable for the dislocation of the strata about them and for their eruption in circular valleys (Pyrmont, Driburg) which are usually completely closed. Friedrich Hoffman and Buckland have almost at the same time very characteristically denominated such depressions valleys of elevation (Erhebungs-Thäler).

In the springs to which the name of sulphurous waters is given, the sulphur by no means constantly occurs combined in the same way. In many, which contain no carbonate of soda, sulphuretted hydrogen is probably dissolved; in others, for example in the sulphurous waters of Aix (the Kaiser, Cornelius, Rose, and Quirinus springs), no sulphuretted hydrogen is contained, according to the precise experiments of Bunsen and Liebig, in the gases obtained by boiling the quantity of oxygen to be only 0.299. We had previously found 0.31 of oxygen in meteoric waters (rain). Upon the nitrogen gas contained in the acid springs of Neris and Bourbon l'Archambault, see the works of Anglade and Longchamp (1834), and on carbonic acid exhalations in general, see Bischof's admirable investigations in his Chemische Geologie, Bd. i, s. 243-350.

55 Bunsen, in Poggendorff's Annalen, Bd. lxxxiii, s. 257; Bischof, Geologie, Bd. i, s. 271.

waters without access of air; indeed the Kaiserquelle alone contains 0.31 per cent. of sulphuretted hydrogen in gas bubbles which rise spontaneously from the springs.5

A thermal spring which gives rise to an entire river of water acidified by sulphur, the Vinegar river (Rio Vinagre), called Pusambio by the aborigines, is a remarkable phenomenon to which I first called attention. The Rio Vinagre rises at an elevation of about 10,660 feet on the northwestern declivity of the volcano of Purace, at the foot of which the city of Popayan is situated. It forms three picturesque cascades, of one of which I have given a representation, falling over a steep trachytic wall probably 320 feet in perpendicular height. From the point where the small river falls into the Cauca, this great river for a distance of 2—3 miles (from 8 to 12 English miles) downwards, as far as the junctions of the Pindamon and Palacé, contains no fish; which must be a great inconvenience to the inhabitants of Popayan, who are strict observers of fasts! According to Boussingault's subsequent analysis, the waters of the Pusambio contain a great quantity of sulphuretted hydrogen and carbonic acid, with some sulphate of soda. Near the source, Boussingault found the temperature to be 163. The upper part of the Pusambio runs underground. Degenhardt (of Clausthal in the Harz), whose early death has caused a great loss to Geognosy, discovered a hot spring in 1846 in the Paramo de Ruiz, on the declivity of the volcano of the same name, at the sources of the Rio Guali, and at an altitude of 12,150 feet, in the water of which Boussingault found three times as much sulphuric acid as in the Rio Vinagre.

The equability of the temperature and chemical constitu

56 Liebig and Bunsen, Untersuchung der Aachener Schewefelquellen, in the Annalen der Chemie und Pharmacie, Bd. lxxix (1851), s. 101. In the chemical analyses of mineral waters which contain sulphuret of sodium, carbonate of soda and sulphuretted hydrogen are often stated to occur from an excess of carbonic acid being present in those waters. 57 One of these cascades is represented in my Vues des Cordillères, pl. xxx. On the analysis of the water of the Rio Vinagre, see Boussingault, in the Annales de Chimie et de Physique, 2e, série, t. lii, 1833, p. 397, and Dumas, 3e série, t. xviii, 1846, p. 503; on the spring in the Paramo de Ruiz, see Joaquin Acosta, Viajes Cientificos á los Andes Ecuatoriales, 1849, p. 89.

tion of springs as far as we can ascertain from reliable observations, is far more remarkable than the instability which has been occasionally detected. The hot spring-waters, which, during their long and tortuous course, take up such a variety of constituents from the rocks with which they are in contact, and often carry them to places where they are deficient in the strata through which the springs burst forth, have also an action of a totally different nature. They exert a transforming and at the same time a formative activity, and in this respect they are of great geognostic importance. Senarmont has shown with wonderful acuteness, how extremely probable it is that many vein-crevices (ancient courses of thermal waters) have been filled from below upwards by

58 The examples of alteration of temperature in the thermal springs of Mariara and las Trincheras lead to the question whether the Styx water, whose source, so difficult of access, is situated in the wild Aroanic Alps of Arcadia, near Nonacris, in the district of Pheneos, has lost its pernicious qualities by alteration in the subterranean fissures of supply? or whether the waters of the Styx have only occasionally been injurious to the wanderer by their icy coldness? Perhaps they are indebted for their evil reputation, which has been transmitted to the present inhabitants of Arcadia, only to the awful wildness and desolation of the neighbourhood, and to the myth of their origin from Tartarus. A young and learned philologist, Theodor Schwab, succeeded a few years ago, with great exertion, in penetrating to the rocky wall from which the spring trickles down, exactly as described by Homer, Hesiod, and Herodotus. He drank some of the water, which was extremely cold, but very pure to the taste, without perceiving any injurious effects (Schwab, Arkadien, seine Natur und Geschichte, 1852, s. 1520). Amongst the ancients it was asserted that the coldness of the water of the Styx burst all vessels except those made of the hoof of an ass. The legends of the Styx are certainly very old, but the report of the poisonous properties of its spring appears to have been widely disseminated only in the time of Aristotle. According to a statement of Antigonus of Carystus (Hist. Mirab. § 174), it was contained very circumstantially in a book of Theophrastus, which has been lost to us. The calumnious fable of the poisoning of Alexander by the water of the Styx, which Aristotle communicated to Cassander by Antipater, was contradicted by Plutarch and Arrian, and disseminated by Vitruvius, Justin, and Quintus Curtius, but without mentioning the Stagirite (Stahr, Aristotelia, Th. i, 1830, s. 137-140). Pliny (xxx, 53) says, somewhat ambiguously:-" Magna Aristotelis infamia excogitatum." See Ernst Curtius, Peloponnesus (1851), Bd. i, s. 194-196, and 212; St. Croix, Examen Critique des Anciens Historiens d'Alexandre, p. 496. A representation of the cascade of the Styx, drawn from a distance, is contained in Fiedler's Reise durch Griechenland, Th. i,s. 400.