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the earthquake of 1693,"numerous long fissures of various breadth were caused, which threw out sulphurous water; and one of them, in the plain of Catania (the delta of the Simeto), at the distance of four miles from the sea, sent forth water as salt as the sea.' The saline character of the water ejected, or said to have been ejected, from volcanoes or earthquake-fissures, has been supposed to support the idea, that the water in such cases is really sea-water, which has somehow been sucked into, and stored up in cavities in, the interior of the earth. Hooker † states, that after certain eruptions of Hekla, salt has been found in such quantities as to load a number of horses. But there is no evidence to prove, either that the water, which flowed in torrents down the sides of Hekla during certain eruptions was saline, or that salt was deposited by its evaporation. These, I fear, are mere tales of the mountaineers, like similar stories anent Etna !

Speaking of fissures made during the celebrated earthquake in Calabria in 1783, Lyell states, "in many instances individuals were swallowed up by one shock, and then thrown out again alive, together with large jets of water, by the shock which immediately succeeded."‡

Sir William Hamilton (in his "Campi Phlegræi," p. 27) says, "It is well attested that in the great eruption of Vesuvius A.D. 1631, several towns, among which were Portici and Torre del Greco, were destroyed by a torrent of boiling water having burst out of the mountain with the lava, by which thousands of lives were lost." Sir William's theory of the origin of this water is, that it is simply rain-water, which has penetrated or permeated the crust of the earth, and has made its way into huge reservoirs in its interior, in which reservoir it has been stored.

2. "Deluges are often caused in the Andes by the liquefaction of great masses of snow, and sometimes by the rending open, during earthquakes, of subterranean cavities filled with water. In these inundations, fine volcanic sand, loose stones, and other materials, which the water meets with in its descent, are swept away, and a vast quantity of mud called 'Moya'

*Lyell's "Principles," p. 503.

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Principles," p. 479.

† Journal of a Tour in Iceland, &c., p. 115.

Quoted by Hooker, p. 113.

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is thus formed, and carried down into the lower regions. Mud derived from this source descended in 1797 from the sides of Tunguragua in Quito, and filled valleys 1000 feet wide to the depth of 600 feet, damming up rivers and causing lakes. In these currents and lakes of moya,' thousands of small fish are sometimes enveloped, which, according to Humboldt, have lived and multiplied in subterranean cavities.* So great a quantity of these fish were ejected from the volcano of Imbaburu in 1691, that fevers, which prevailed at the period, were attributed to the effluvia arising from the putrid animal matter."†

In January 1803, the vast mass of snow, which usually covers Cotopaxi, in South America, was suddenly dissolved in a night. "In Quito, on the 19th of July 1698, during an earthquake, a great part of the crater and summit of the volcano Carguairazo fell in, and a stream of water and mud issued from the broken sides of the hill."‡

During the earthquake in Peru, on 28th October 1746, a volcano broke out in Lucanas," and such quantities of water descended from the cone that the whole country was overflowed; and, in the mountain near Pataz called Conversiones de Caxamarquilla, three other volcanoes burst out, and frightful torrents of water swept down their sides."§

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During the earthquake, which destroyed Caraccas (on 26th March 1812), an immense quantity of water was thrown out at Valecillo,, near Valencia, as also at Porto Cabello, through openings in the earth; and in the Lake Maracaybo the water sank." The latter is the sort of coincident phenomenon, which is eagerly seized upon as an illustration of the correctness of the theory of those, who assert the connection between the water ejected in the course of volcanic eruptions or earthquakes and that of lakes or rivers. That there may be a connection in certain rare instances is possible; but this, not being a subject properly coming within the scope of this paper, I can only refer to it en passant.

*The presence of fish has been regarded by other writers as a proof that the water ejected from volcanic craters or earthquake-fissures was originally the water of rivers, lakes, or the sea, which had been sucked into the interior of the earth by suddenly formed cracks or otherwise.

Lyell's "Principles," pp. 348 and 469.

2 Ibid. p. 501.

Ibid p. 503.

|| Ibid. p. 465.

In the course of the earthquakes in South Carolina and in New Madrid, Missouri, in 1811-12, "the inhabitants relate that the earth rose in great undulations; and when these reached a certain fearful height, the soil burst, and vast volumes of water, sand, and pit-coal were discharged as high as the tops of trees."*

Numerous fissures were produced in Jamaica by the earthquake of 1692. "Many people were swallowed up by these rents; some the earth caught by the middle, and squeezed to death; the heads of others only appeared above ground; and some were first engulfed, and then cast up again with great quantities of water."t

3. "The town of Chittagong, in Bengal, was violently shaken by an earthquake on the 2d of April 1762, the earth opening in many places, and throwing up water and mud of a sulphureous smell." +

In the Runn of Cutch, India, in 1819, jets of black muddy water were ejected from fissures caused by an earthquake-the water containing " numerous pieces of wrought-iron and ship nails!" §

During the volcanic eruption in the Island of Sumbawa, in April 1815," in the Island of Amboyna, in the same month and year, the ground opened, threw out water, and then closed again." ||

In Java, in 1822, the mountain Galongoon (or Galung Gung) suddenly became an active volcano. On the 8th October "a loud explosion was heard; the earth shook, and immense columns of hot water and boiling mud, mixed with burning brimstone, ashes, and lapilli of the size of nuts, were projected from the mountain like a waterspout, with such prodigious violence, that large quantities fell beyond the river Tandoi, which is forty miles distant. Every valley within the range of this eruption became filled with a burning torrent; and the rivers, swollen with hot water and mud, overflowed their banks, and carried away great numbers of the people, who were endeavouring to escape, and the bodies of cattle, wild beasts, and birds. A space of twenty-four miles

*Lyell's" Principles," p. 466.
Ibid. p. 494.

§ Ibid. p. 464.

† Ibid. p. 504.

Ibid. p. 465.

between the mountain and the river Tandoi was covered to such a depth with bluish mud that people were buried in their houses, and not a trace of the numerous villages and plantations throughout that extent was visible. . . . It was remarked that the boiling mud and cinders were projected with such violence from the mountain, that, while many remote villages were utterly destroyed and buried, others much nearer the volcano were scarcely injured.

At the end of four days a second eruption occurred, more violent than the first, in which hot water and mud were again vomited, and great blocks of basalt were thrown to the distance of seven miles from the volcano."* †

* Lyell's "Principles," p. 430.

† Should the reader wish-further than the bibliographical references already contained in this paper enable him-to compare the accounts of the eruptions of other Icelandic volcanoes with those of Kötlugjá, he may consult the following works :

1. "Annales Islandorum Reg.," in Langenbeck's "Scriptores rerum Danic. medii ævi," which contains an account of the earlier eruptions in Iceland.

2. "Letters on Iceland," &c., by Uno Von Troil, D.D., Chaplain to his Swedish Majesty, &c. London, 1780; the prefix whereof (pp. 18 and seq.) contains a bibliographical list of 120 works on Iceland, some of which treat wholly or partly of volcanic phenomena.

3. Bishop Finnsen's " Efterretning om Tildragelserne ved Bierget Hekla ;” Copenhagen, 1767.

4. "Kort Beskrivelse over den nye Vulcans Ildsprudning i Vester Skaptafjeld's Syssel paa Island i aaret 1783;" being an account of the eruption of the Skaptar-jökul, by Magnus Stephenson, Etatsroed of Iceland, with engravings, 8vo; Copenhagen, 1785. Translated in Hooker's "Journal of a Tour in Iceland," vol. ii. p. 124.

5. S. M. Holme “Om Jordbranden paa Island i aaret 1783;" Copenhagen, 1784.

6. Garlieb, "Island rucksichtlich seiner Vulkane;" Freiburg, 8vo, 1819. 7. Hekla og den sidst Udbrand den 2 Septem. 1845. En Monographie : med 10 Plader Lin. 8vo, Copenhagen, 1847, by J. C. Schythe. A brochure on the most recent Eruption of Hekla, costing about 3s. in this country.

On the Claim of Dr Wells to be regarded as the Author of the " Theory of Dew." By CHARLES TOMLINSON, Lecturer on Science, King's College School, London.

Probably there never was a scientific treatise at once so famous and so little known, as the "Essay on Dew," by William Charles Wells, M.D., published in 1814. A second edition of this treatise appeared in 1815, and a third in 1818, containing the author's autobiography written shortly before his death, which took place in September 1817. The essay excited some discussion during the author's lifetime. Some of the leading facts, together with an epitome of his "Theory of Dew," were at once adopted in books on natural philosophy, and these have been repeated, with little or no variation, by every writer on physics down to the present time.

What then has made Wells' "Essay on Dew" so famous, if at the same time it is so little known? It is but little known, because it has long been out of print, and therefore inaccessible to the readers of popular science; it is famous, because the innumerable books on natural philosophy have referred to it with applause, but chiefly because one of our most celebrated scientific authorities has pointed out this essay as a model of inductive experimental inquiry. Sir John Herschel, in his "Preliminary Discourse on the Study of Natural Philosophy," characterises Wells' essay as "one of the most beautiful specimens we can call to mind of inductive experimental inquiry lying within a moderate compass;" and he earnestly recommends it to the student of natural philosophy" as a model with which he will do well to become familiar."*

* Dr Lardner also, in his "Treatise on Heat" (1833), gives unbounded credit to Dr Wells. He says:-" The result of his inquiries was the discovery of the cause of the phenomena of dew, and affords one of the most beautiful instances of inductive reasoning which any part of the history of physical discovery has presented" (p. 328). In another Treatise on Heat, published in 1855, Dr Lardner still gives the whole credit of the "celebrated Theory of Dew to Dr Wells. Dr Golding Bird, in his "Elements of Natural Philosophy," 4th edit., 1854, also gives the whole credit to Wells. French and German treatises do the same. Thus Eisenlohr "Lehrbuch der Physik," 1860, in describing the capital experiment of two thermometers, one on the ground, and the other in the air, marking different temperatures, says, "Dieser Versuch rührt von Wells her," p. 367.

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