Within the last few months Prof. Silvestri has detected a mineral oil in the cavities of a prehistoric doleritic lava found near Paterno.[21] The lava is in close contiguity to the clay deposits of a mud volcano, and when examined under the microscope is seen to consist mainly of augite, together with olivine and transparent crystals of labradorite. It contains numerous cavities coated with arragonite, and filled with a mineral oil which constitutes about one per cent of the whole weight of the lava. It was taken from the lava at a temperature of 24° C., (75·2° F.), and solidified at 17° C. (62·6° F.) to a yellowish green mass, which on analysis gave the following percentage composition:-- Liquid hydrocarbons boiling at 79° C. = 17·97 Hydrocarbons solidifying below 0° C., boiling } between 280° and 400° C. } = 31·95 Paraffine melting between 52° and 57° C. = 42·79 Asphalt containing 12 per cent of ash = 2·90 Sulphur = 4·32 ------ 99·93 [21] "Atti Accademia Gioenia," serie iii., vol. xii. Prof. Silvestri has recently made some interesting determinations of the specific gravity and chemical composition of the different products of Etna. They are given in full in his work entitled, "_I Fenomeni Vulcanici presentati dall'Etna, nel 1863, 1864, 1865, 1866_," which was published in Catania in 1867. The following table gives the specific gravity of various ancient and modern forms of lava, ashes, etc. of Etna:-- _Sp. Gr._ Ashes ejected in 1865 2·644 Sand " " " 2·715 Scoriæ " " " 2·633 Compact lava " " 2·771 Scoriæ ejected in 1669 2·622 Compact lava " " 2·697 Lapilli ejected in 1444 2·420 Compact lava ejected in prehistoric times 2·854 A very decided change in the specific gravity was found to take place after fusion. This can only be accounted for on the supposition that a chemical change is effected during the fusion:-- _Sp. Gr._ _Sp. Gr._ _before fusion._ _after fusion._ Pyroxene of Etna 3·453 2·148 Felspar " " 2·925 1·361 Olivine " " 3·410 2·290 Lava of 1865 2·771 1·972 Ancient basaltic lava from } 2·854 2·000 the Scogli de'Ciclopi } Ancient basaltic lava from } 2·795 1·947 Aci Reale }