t, than for the changes they have produced on the surface. ngs of St. Michael. The hot springs of St. el, one of the Azores, have been long celebrated. waters rise from among volcanic rocks, and hold quantities of silex in solution. As the waters derom the fountain, they deposite their silex in the f what is termed silicious sinter, which may be red as answering to the travertine, or tufa, of calcaprings. herbage and leaves along the course of the stream re or less encrusted with silex, and exhibit all the ive steps of petrifaction, from a soft state to a comonversion into stone. Branches of ferns, such as ow in the vicinity, are thus changed, still preservir appearance of vegetation, except that they have d an ash grey colour.-Dr. Webster, Ed. Phil. thrown up from the pi the height of from one load explosions. This ke an artificial fountai he same time giving off rapor, when the pipe whole contents of wa column of steam, which and a loud thundering paroxysm terminates, an If stones are thrown eration, they are instan are force of the steam, are returned into the Mr. Henderson, late a painted with these ph ones into the pipe of ruption in a few minut ents of stone as well higher than usual. W n in this manner, and team continued to rus aded by a deafening Geyser, as if exhausted toms of a fresh elapsed In the different expla count for phenomena which have been no w gree in supposing steam collect, and interrupted force to overcome the at interv Site of the water. Thi mered diagram, red remark that the theory ng spring, only that t her is s explained Author's Nat. Philoso ers of Iceland. But the Geysers of Iceland afford st remarkable examples of the deposition of silex. springs are situated in a volcanic district, the surthe ground out of which they rise being covered reams of ancient lava, through the fissures of which, and hot water, are emitted in various places. great Geyser, which has excited so much interest, ount of the singular phenomena which it exhibits, ut of a basin at the summit of a circular mound, sed of silicious incrustations deposited from the of its waters. The diameter of this basin or crater eet in one direction, and 46 in the other. ne centre of this basin is a natural pipe seventyeet in perpendicular depth, and from eight to ten diameter, gradually widening as it opens into the The basin, as the spring intermits, is sometimes but is more commonly filled with beautifully transboiling hot water, which is often in a state of vioullition. During the rise of the water up the pipe, lly when the ebullition is most violent, subterraoises are heard, like the distant firing of cannon, slight tremor of the earth is felt near the place. -und then increases, and the motion of the earth be more violent, until at length a column of water is erupt a on th com the pipe, in a perpendicular direction to f from one to two hundred feet, attended with ons. This is continued, with interruptions icial fountain, for a few minutes, the water at e giving off immense quantities of steam and the pipe is evacuated by the discharge of ntents of water, and there follows an immense team, which rushes up with amazing force hundering noise, after which the eruption, or rminates, and the Geyser becomes quiet. are thrown into the pipe, or crater, during an y are instantly ejected, and such is the explothe steam, that masses of hard rock thrown ned into the air, shivered into small fragments. son, late a resident in Iceland, and well ach these phenomena, states that by throwing the pipe of the Geyser, he could bring on an a few minutes, and that in such cases the fragone as well as the water were thrown much usual. When an eruption had been brought nanner, and the water had been ejected, the nued to rush up, with amazing force, and atdeafening roar, for nearly an hour, but the f exhausted by this effort, did not give sympfresh eruption when its usual interval had ferent explanations which have been offered to phenomena so singular and astonishing, and been no where else observed, most writers pposing a subterranean cavity, where water Ollect, and where the free escape of the steam d at intervals, or until it acquires sufficient rcome the resistance occasioned by the preswater. This will be readily understood by the gram, reduced from Mr. Lyell, and we may the theory is the same with that of intermitonly that the Geyser acts by steam, while the lained on the principles of the syphon.-See the at. Philosophy, p. 107. way into the subterranean cavity d, by the fissures f f, while at the same time steam of an high temperature, emanates from volcanic rocks me cavity through the fissures c c. A portion m in the first place would be condensed into ts temperature continuing to increase by the of the steam, the lower part of the cavity would ed with the boiling fluid, while the upper part filled by steam under considerable pressure. continuing to form, the water being now too dense it, would soon by its expansive force, water up the pipe or fissure e, b, whatever ts height, and thus the basin at the surface lled, and an eruption take place. When the thus diminished, the steam in the upper part of z, would expand, or probably a portion of the er under diminished pressure would be instantd into steam, and the passage being free, would è pipe in the same manner as is seen and heard the safety valve of a steam boiler. If the ked up artificially with stones, even for a few great increase of heat would be occasioned, eam would thus be prevented from escaping, water would be made to boil in a few minutes eruption would be brought on, as stated by rson. planation accounts for all the phenomena obie Geysers, and although we cannot be certain still there is every reason to believe that such The Rhone enters at one Genera stands at the o charges itself near the ci parent, but at the upper 6 quence of the matter b Mr. De La Beche, afte e depth of the water in hundred and twent ms; but on approac he water began to gro mile and three quarter ay be stated therefore the river are about t gs it has been ascerta psites from the Rhon undred feet in thickne Roman buildings judges that this accumu eight hundred on t years. eph of this accumula ties, we should see a 3, and it is certain that steam is the moving forms a theory of earthquakes on this expla Seat and Theory of Earthquakes. DELTAS IN LAKES. le changes have taken place by causes now consequence of the deposition of earthy mouths of rivers where they enter lakes, or ve already given an account of the accumualong the shores of the Adriatic in consey of depositions from the river Po. The atter thus carried down by different rivers, gnitudes, differs exceedingly; this difference uch on the rapidity of the stream, and its erflow its banks at certain seasons. e Lake of Geneva. The Lake of Geneva is niles long, and from two to nine miles broad. enters at one end of this lake and the city of Is at the other. The water where it disnear the city is exceedingly clear and transthe upper end it is commonly turbid, in conne matter brought down by the Rhone. Beche, after numerous soundings, found that he water in the middle of the lake was from and twenty, to one hundred and sixty faon approaching the mouth of the Rhone, gan to grow shallower at the distance of a ee quarters from that end of the lake. It therefore that the strata annually produced re about two miles in length. From soundeen ascertained that in some places the dethe Rhone are probably from six to nine in thickness; and from the remains of some ings on the border of the lake, Mr. Lyell is accumulation has taken place within the last d years. "If," says he "we could obtain the accumulation formed in the last eight centu=ld soo a croat series of strata probably from ne hundred feet thick, and nearly two miles in nclined at a very slight angle." yell proposes a plan for estimating the time when of Geneva, or the Leman Lake will become dry he accumulations from the Rhone. capacity of the lake being obtained, "it would," "be an interesting subject of inquiry, to deterwhat number of years the Leman lake would be d to dry land. It would not be difficult to obtain ents for such a calculation, so as to approximate to the quantity of time required for the accomat of this result. The number of cubic feet of nually discharged by the river into the lake being experiments might be made in winter and summer nine the proportion of matter held in suspension, emical solution, by the Rhone." calculations, however, after all the data that could ned, would be exceedingly uncertain, and since nents proposed by the author have not been we do not extract his speculations on this DELTAS Accumulations in the he waters of the Baltic se ey have remained station oversy since the middle Swedish astronomer, atten this sea had suffered a y-five inches in a centu ended that the proof modern observations, geographers, who insula, was formerly s of Celcius and his ciently distinguish bet the deposition of sedim sea. It appears that the chiefly vere it ascertained exactly how much alluvial s carried down by the Rhone at the present day, would decide nothing definitely with respect to during which this accumulation has been forming. ng to Mr. Lyell's supposition above cited, a part elta has formed at the rate of about a foot in a year, from six to nine hundred feet in eight hundred Now allowing that the Rhone has, on an average, 1 a foot of matter a year in the lake, and has cono do so ever since the deluge, then the accumulaht to be at least four thousand feet thick, which ong ago have filled up the Leman lake, and made ground. The phenomena of this lake, therefore shows that either it has not received the Rhone any years, or if so, that its waters contained less atter anciently than at present. In either case, e certain that no argument can be derived from ent condition of this delta, in favour of the high of the present form of the earth. But on the conany conclusions can be drawn from this source, in direct coincidence with the idea that the preer of things are of recent origin, and therefore in tion of the truth of the sacred history of the deluge. mates were a ma din bays, where in the ore attention. Thus it accun But since it was possil unted for by the Pression of the waters, ment still for his theo lar rocks in the g tirely covered by wat had risen in the course below the water to the |