564 Notices of Memoirs—W. W. Watts—LIgneous Rocks. 
INi@ ihe ES) Cy Var VE@rsre S- 
J.—Norse on THE OccurreNncE or Levcrre at Erna.! By H. J. 
Jounston-Lavis, M.D., F.G.S. 
Sree years since, whilst on a visit to Etna, my attention was 
drawn to some superficially placed tuffs of a chocolate to a 
coffee-brown colour. In these tuffs, near the Casa del Bosco, are 
observable included pieces of scoriaceous lava which to the naked 
eye are evidently leucitic; that mineral occurring in well-formed 
crystals attaining to some millimetres in diameter, and brilliantly 
white as the result of fairly advanced kaolinization. In consequence 
of this change the rock is excessively friable, and, therefore, difficult 
to sectionize. A section of it, however, was exhibited at the meeting, 
and also two photo-micrographs therefrom. In these it will be seen 
that kaolinization has extended along the fracture planes of the 
leucites, whilst the beautifully formed pyroxene crystals are unaltered, 
and the triclinic felspars are fairly in a normal condition. The base 
is a microlitic net-work of felspar and pyroxene, together with 
beautifully minute cubes and octahedra of magnetite, rendering the 
substance intervening between the crystals almost opaque, even in 
thin sections. The pyroxene is often enveloped in a casing of leucite, 
as at Vesuvius, Roccamonfina, etc., confirming what I have asserted 
in other places, namely, that leucite is one of, if not the latest mineral 
to crystallize. 
T regret that I have not the opportunity of investigating the question 
of the origin and age of this rock more completely, as on writing 
to my friend Prof. O. Silvestri, inquiring if leucite had yet been 
encountered at Etna, I received a categorical answer in the negative 
which, coming from such an authority, must be taken as conclusive 
as to the rarity of leucitic rocks being produced from Ktna. 
The discovery of this mineral at Etna is what one would have 
looked for, knowing as we do its wide distribution in nearly all the 
other late basic volcanoes of Italy. 
II.—An Icanrous Succession 1n Suropsuire.! By W. W. Warts, 
M.A., F.G.S., Fellow of Sidney College, Cambridge. 
ie author described the succession of igneous rocks in the Shelve 
and Corndon district of Shropshire. 1. There is a series of 
andesitic ashes interbedded at two principal horizons in the Ordo- 
vician sequence. These have a percentage of silica varying from 
63-60. 2.Then come three sets of intrusive masses. a. Andesites 
(59-54 per cent. of silica); these are intruded into Ordovician 
rocks and never touch the Silurian of the district. 6. Dolerites (49- 
47 per cent. of silica), which are post-Silurian in date. ¢. Picrites 
(40-84 per cent. of silica), of later date. There are undoubtedly rocks 
intermediate in age and composition, but it is difficult to be quite sure 
of this where the differences in composition are so slight. One, 
1 Read before Section C. (Geology) British Association, Bath, September, 1888. 
