von Lasaulx, from specimens taken from the oldest (vorätnäischen) sheets of lava down to those of the present day, indicates a rock of remarkable uniformity of composition, in which the components are plagioclase felspar, augite, olivine, magnetite, and sometimes apatite; but of leucite we have no trace.[9] In fact, the lavas of Etna are very much the same in composition as the ordinary basalts of the British Isles, while those of Vesuvius are of a different type. This seems to suggest an origin of the two sets of lavas from a different deep-seated magma; the presence of leucite in such large quantity requiring a magma in which soda is in excess, as compared with that from which the lavas of Etna have been derived.[10] [1] _Mémoires pour Servir_, etc., vol. ii. [2] Daubeny, _Volcanoes_, p. 270. [3] Von Waltershausen, _Der Ætna_, edited by A. von Lasaulx. [4] Lyell, _Principles of Geology_, vol. ii., edition 1872. [5] Its height, as determined by Captain Smyth in 1875 trigonometrically, was 10,874 feet, and afterwards by Sir J. Herschel barometrically, 10,872 feet. [6] _Atlas des Ætna_ (Weimar, 1858), in which the different lava-streams of 1688, 1802, 1809, 1811, 1819, 1824, and 1838 are delineated. [7] Sir William Hamilton observes that history is silent regarding the first eruptions of Etna. It was in activity before the Trojan War, and even before the arrival of the "Sizilien" settlers. Diodorus and Thucydides notice the earliest recorded eruptions, those from 772 to 388 B.C., during which time the mountain was thrice in eruption. Later eruptions took place in the year 140, 135, 125, 122 B.C. In the year 44 B.C., in the reign of Julius Cæsar, there was a very violent outburst of volcanic activity.--_Neuere Beobachtungen über die Vulkane Italiens und am Rhein_, p. 173, Frankfurt (1784). [8] "Report on the Chemical and Mineralogical Characters of the Lavas of Vesuvius from 1631 to 1868," _Transactions of the Royal Irish Academy_, vol. xxvi. (1876). In the lava of 1848 leucite was found to reach 44.9 per cent. of the whole mass. In that of Granatello, 1631, it reaches its lowest proportion--viz., 3.37 per cent. [9] A. von Lasaulx, in Von Waltershausen's _Der Ætna_, Book II., x. 423. [10] The view of Professor Judd, that leucite easily changes into felspar, and that some ancient igneous rocks which now contain felspar were originally leucitic, does not seem to be borne out by the above facts. In such cases the felspar crystals ought to retain the forms of leucite. See _Volcanoes_, 4th edition, p. 268. CHAPTER III. THE LIPARI ISLANDS, STROMBOLI.