SILICA. 
IGD 
122i Portion of irregular fill¬ 
ing of ^ fissure with Amethyst and 
Agate-jasper, the latter showing 
imprintfe of the Amethyst crystals. 
Gdgenberg. 
123. Fragment of a large 
Amygdaloid, with coating of Pe- 
lessite, aad filled with Agate-jas¬ 
per, Amethyst, and Barytes. 
IldJu Leiter, near Oherstein, 
124. Fragment of a Vein for¬ 
mation. IIoRNSTONE intersected 
by threads of Carnelian. 
Galgcnberg. 
125. Fissured Meladhyre inter- 
Horse-siioe Case — continued. 
Case L. 
sccted by threads of Chalcedony 
and Carnelian. 
Galgcnberg. 
126 to 130. Specimens of differ¬ 
ent varieties of the Melapiiyre, 
or Augitic Porphyry, which con¬ 
tains Amygdaloids. 
In the district of Oberstein. 
131. Melaphyre. 
Wiesselberg, near St. Wendel. 
132. Amygdaloidal Mela- 
PHYRE. 
Scotland. 
(In this case are placed some impres¬ 
sions illustrating Dr. Franz Ley dolt’s 
process of printing fi’om etched Agates.) 
Silica, amorphous and hydrous. 
794. Silica Eock,” or Fire- , 
stone,” extensively used as a ma- ' 
nure, and said to. contain from 30 
to 70 per cent, of silica soluble in 
alkalies. {See Journ. Agric. Soc., 
vol. xiv., p. 225). 
From the Lower Greensand, Farn- { 
ham, Surrey. 
Presented, by J. M. Paine. 
795. Flexible Saxdstoxe. 
Jvjjur, 120 miles A. TF. fro7n 
Delhi. 
Pre.sented by Col. Guthrie. 
796. Saxdstoxe, furrowed by 
the action of drift sand. 
Sinai Peninsida. 
Presented by Major Macdonald. 
797. Saxdstoxe, in cubic forms, 
pseudomorphous after crystals of. 
Eock Salt. 
From the Purbeck beds. Cliffs E. 
of Lulwoi'th Cove, Dorsetshire. 
Contributed by the Geological Survey. 
797a. IIorxstoxe, in octolie- 
dral forms, pseudomorphous after 
crystals of Fluor Spar. 
Gwennap, Cornwall. 
798. Fulgurites, or “ Fossil 
Lightning.” Vitrified sand tubes 
produced by the action of light- 
ning. 
JS'atal, S. Africa. 
799. Chert, used for paving- 
stones for the flint-grinding mills 
in the Stafibrdshire potteries. 
Fi'07n the Millstone G7dt, Pe7i-y7'~ 
he7iblas, 7iear Holywell, Flint¬ 
shire. 
800. Baxded Chert, in Car¬ 
boniferous Limestone. 
Near Matlock, Derbyshire. 
801. Baxded Chert, in Car¬ 
boniferous Limestone, polished. 
Near Matlock, De7lyshire. 
802 and 803. Chert, contain¬ 
ing casts of fossils {Producta and 
Spirifer'). 
From the Carbonife7'ous Li/nesto7i€, 
Matlock Bath, De7'byshire. 
804. Flixt, showing well the 
conchoidal fracture. 
Whit77iore, near Weymouth, 
