light, and they are not fusible in fire.

Gemellaro gave me a paper of them when I was with him. The eruptions are unquestionably due to a superabundance of moisture: when the water is decomposed explosive gases result. Hence, earthquakeshocks generally coincide with the throes of the mountain. A very wet season is always followed by one dangerous to those who dwell near a volcano: it has been noted also that in the first stages of an eruption streams of salt water are sometimes vomited. Volcanoes, moreover, throughout the known world, stand in the vicinity of scas, as Cotopaxi, Hecla, Etna, Vesuvius, &c. Stromboli is in the sea. Some one has observed that where a sca has retired, or the inland lake dried up, the volcano has become extinct. Now all this dangerous activity of the water would alone lead one to think of clay as the base; for that substance is impervious to water, and when the chambers within the mountain's jaws are heated they act as boilers and generate steam. There is another and distinct reason for assuming a base of clay, and that is the apparent fact that old lavas return to the state of clay, as is seen in the Solfaterra. Having said this it is fair to mention one objection to clay being

supposed the prevailing ingredient, which is this: clay is very cold, but the lava torrents retain their heat sensibly for a number of years. The current of 1669, I am assured, was warm in parts for ten years afterwards: and that of 1843 is hot now, at the end of two winters, on the Bronte side of the mountain. This difficulty is very great: but may be met by the fact that metal, which radiates very slowly, is present in the formation. I think, however, there is another consideration which may solve the problem.

The lava-rock would appear to possess the property of internal combustion, as a piece of phosphorus docs. Whoever has read that very interesting book the "Etudes sur la Nature," will remember a chapter there on origins and species, by B. St. Pierre, in which he remarks, contrà the geologists, that Etna's forges must have been formed before an eruption could take place. I quote from memory and have no copy of the work within reach: but his argument is unanswerable, and will bear as a corollary [note (f)] that there must have been fuel in the forge from the first. In brief, the fusion results from fire kindling within the rock itself, when the viscous nature of the substance and its

aversion to assuming a gascous form, cause the fluid stream of stony matter. A chemist would say there is a reaction of the component elements of the rock, as in the case of fermentation.

Switzerland has glaciers, but no volcanoes; why? because it is inland. Its fresh-water lakes would not feed a volcano. The "fall of the Rossberg," however, was accompanied by an explosion of gas, a shower of heavy missiles, and an exuding of vast masses of clay; which had every volcanic character save the phosphoric and metallic one of melted matter flowing as from a forge.

While speaking on the subject of the lava, I may note here what has been found to be the chief danger attendant on approaching a stream of it in motion. This danger lies in any covered tank or reservoir of water happening to be near. In one of the latest eruptions of Mount Etna a number of persons had followed the course of the lava for some miles, occasionally stirring it with sticks, and even running across the heated current. At a certain point, the stream came in contact with a small reservoir; an explosion of steam followed instantaneously, and about a score of persons who were standing near lost their lives; others were scalded.

The same thing occurred not very long ago on Vesuvius.

Among the specimens of lava which I collected while in Catania, I have one exhibiting a transparent agate-like substance, striped as are the Scotch pebbles: this was without doubt formed by the heated lava thus coming in contact with water.

While on this subject, I mention a fact unwelcome to divers modern geologists. The origin of basalt is probably aqueous; a variety which is evidently stalagmitic may now be scen in a cliff near Aci-Trezza on this coast. The Cyclopean Isles hard by are of this material. We have made our trip there, but a rough sea forbad our landing on the sheer rock. In the attempt we were nearer being drowned than I ever saw a boat's crew in my life. "Non nobis, Domine!" said I, and say still. The "temporale" came like lightning, the waves rose like a castle wall, our boatmen were panicstruck, and our fat host, Abbate, very near upset us all. My servant, a Florentine, turned as pale as if he had seen the Angel of Death.

SYRACUSE.

Syracuse, January, 1846.

WE paid a visit to Messina a week ago, where we had the pleasure of being wind-bound on Christmas day. As the breeze still continued adverse for Naples, and a steamer here on such occasions is only another word for your coffin, we have run down the coast thus far to get a peep at scenes renowned in the annals of Athens and consular Rome.

Messina has not many lions, but it seemed a comfortable sort of place to live in. From the brow of a mountain behind the town there is a noble view of the two seas, Tyrrhene and Ionian. On the quay stands one fine piece of sculpture, a fountain with sirens. There are three or four splendid convents: in that of " Monte Alto" I found an entire wall covered over with votive offerings in descriptive pictures, which is the old Roman custom of Horace's day surviving to our century:

"Me tabulâ sacer

Votivâ paries indicat uvida

Suspendisse potenti

Vestimenta maris Deo."