296 
Proceedings of the Royal Society of Edinburgh. [Sess. 
felspars that those noted by him were always much decomposed. Those 
in the residues under consideration are remarkable for their freshness ; 
the twinning is clearly visible, and in this they resemble the felspars from 
the chalk of the north of France described by M. Levy. All the tourmaline 
occurs as stumpy prisms and is not acicular, as is much of the tourmaline 
found in other sedimentary rocks. The garnet shows no crystalline form. 
The hornblende is an actinolitic and not a basaltic variety, as previously 
described from chalk residues.” 
The scarcity of glauconite in the residues is remarkable especially in 
those which contain most terrigenous material. The explanation may be 
that these chalks were laid down in a considerable depth of water, a fact 
which the Foraminifera tend to confirm. Fragments of iron oxide, usually 
so common in the English chalk, are also rare. Minute spherules and 
cylindrical lengths of iron pyrites and marcasite occur in some profusion in 
B 5, and a few small spherules in A 5. 
No attempt was made to estimate the percentage of mineral grains in 
each residue, but they were more abundant in every specimen than in any 
English chalk above the zone of Amm. Varians. In size they equalled and 
sometimes exceeded those found in the most sandy of our chalk marls.* 
* Mr Hill’s collection lias been presented to the British Museum by Mrs Hill and 
Mr Arthur Hill. 
(Issued separately December 14, 1915.) 
