296 ANNUAL OF SCIENTIFIC DISCOVERY. 



logically inferred that all great volcanic mountains owe their conical form 

 principally to upheaval, or to a force acting from below and exerting an 

 upward and outward pressure on beds originally horizontal or nearly horizon- 

 tal. For in all such mountains there are found to exist some stony layers 

 dipping at 10, 15, 25, or even higher angles; and according to the assumed 

 law, such an inclined position of the beds must have been acquired subse- 

 quently to their origin. 



Sir Chas. Lyell, in a recent communication to the Royal Society, after giv- 

 ing a brief sketch of the controversy respecting " Craters of Elevation," 

 describes the result of a recent visit to Mount Etna, in company with Signor 

 Gcmmcllaro, and his discovery there of modern lavas, some of knoAvn date, 

 which have formed continuous beds of compact stone on slopes of 15, 30, 

 38^, and, in the case of the lava of 1852, more than 40. The thickness of 

 these tabular layers varies from li feet to 26 feet; and their plains of strat- 

 ification are parallel to those of the overlying and underlying scoria? which 

 form part of the same currents. 



An attempt is then made to estimate the proportional amount of inclina- 

 tion which may be due to upheaval in those parts of the central nucleus of 

 Etna where the dip is too great to be ascribed exclusively to the original 

 steepness of the flanks of the cone. The highest dip seen by the author 

 was in the rock of Musarra, where some of the strata, consisting of scoriae 

 with a few intercalated lavas, are inclined at 47. Some masses of agglom- 

 erate and beds of lava in the Serra del Solfizio were also seen inclined at 

 angles exceeding 40. Some of these instances are believed to be exception- 

 able, and due to local disturbances; others may have an intimate connection 

 with the abundance of fissures, often of great width, filled with lava, for such 

 dikes are much more frequent near the original centres of eruption than at 

 points remote from them. The injection of so much liquid matter into 

 countless rents may imply the gradual tumefaction and distention of the vol- 

 canic mass, and may have been attejided by the tilting of the beds, causing 

 them to slope away at steeper angles than before, from the a'xis of eruption. 

 But instead of ascribing to this mechanical force, as many have done, nearly 

 all, or about four-fifths of the whole dip, Sir C. Lyell considers that about 

 one-fifth may, with more probability, be assigned as the effect of such move- 

 ments. 



From various data, discussed at length in the memoir, Sir C. Lyell con- 

 cludes, first, that a very high antiquity must be assigned to the successive 

 eruptions of Etna, each phase of its volcanic energy, as well as the excava- 

 tions of the Val del Bove, having occupied a lapse of ages, compared to 

 which the historical period is brief and insignificant; and secondly, that the 

 growth of the whole mountain must nevertheless be referred, geologically, 

 to the more modern part of the latest Tertiary epoch. 



ILLUSTRATIONS OF SURFACE GEOLOGY. 



In a memoir, under the above title, communicated to the 9th volume of 

 the Smithsonian contributions to knowledge, by Pres. Hitchcock, the author 

 presents the results of a large amount of personal examination, made mainly 

 in New England, though to some extent also in other countries. The heights 

 and positions of numerous terraces along the Connecticut valley and some of 

 its tributaries, and some on the Merrimack river, are given in the text, and 

 the plates contain illustrations both by sections and neat maps. The great 



