76 
remains of marine animals, which become exposed, owing to 
the gradual erosion of the crystals by water—thus showing that 
the mineral is soluble in water, and particularly soin brine. A 
crystal with bright faces was eroded in the same manner as 
those of Egypt, by immersion in a saturated solution of salt for 
18 months. Many of our specimens from Yate, in Gloucester- 
shire, in possession of the writer, are eroded in the same 
manner as those from Egypt. On the faces of some of these 
crystals the erosive action has left markings in the form of 
elliptical rings of about two millimétres in the axis major: 
these marks in most crystals containing water of crystallization 
are caused by weathering. 
The erosion begins by a dull spot forming on a face. This 
gradually spreads in a circle, or an ellipse, until finally it 
occupies the whole face. Pape,* who has investigated the 
nature of these figures, finds that they are circles on crystals of 
the cubic system, but on the faces of rhombic crystals like 
Celestite, they are ellipses. 
Baryto-CeLEstineE.—Baryto-celestine of Walterhausen, is 
an amorphous combination of both sulphates of these minerals. 
From Greiner, in the Tyrolese Alps, the proportions of the 
bases of the mineral are—Celestite 4, Barytes 38. Another 
locality for it is Imfeld in Binnenthal, in Switzerland, Jocketa 
in Saxony, where it is near Dolomite in tale schists. Also (see 
page 1) at Clifton, in Gloucestershire. 
The number of places mentioned as having credit for the 
productions of the Strontian mineral will be considered fairly 
sufficient thus far, without multiplying instances; but one spot 
in particular, namely, Sicily, seems to throw more light upon 
the subject than any other named. Celestite is nearly always 
accompanied by one or more associates, namely, gypsum, 
sulphur, and salt; and in that island, owing to the workings in 
the grey marls of Tertiary age, ample opportunities are offered 
to the geologist or mineralogist such as are not found anywhere 
else. From the first the island has been the scene of volcanic 
* Juke’s Geology (Geikie’s edition), Weathering, page 45 ; also Pogg. 
Annalen., Vol. CKXIV., p. 329 ; and Vol. CKXV., p. 513. 
