LOWER CHALK—MTCROGRAPHTC STRUCTURE. 323 
Grains of Quartz measuring '60 mm. occurred in the Cerne 
Abbas and South Cave examples, but the size seems exceptional, 
and only one or two grains in each case were so large as this, the 
remainder being small, not exceeding ‘2 mm. 
Secondary Minerals. — One or two grains of Glauconite 
occurred in the residue and washings of the Cerne Abbas 
specimen. Dr. Hume says that a few rods of glauconite occurred 
in the sample from Eastbourne, and a few grains in that from 
Swanage. Limonite and irregular masses of porous iron oxide 
were noted in the specimens from Eastbourne, Hitchin, and Dover. 
Summary of Chemical Results. 
The results of the treatment of six specimens of this zone with the 
acid solution are recorded in the annexed table. One of these is 
from Dr. Hume’s Chemical and Micro-Mineralogical Kesearches, 
and two others are from notes kindly sent us by Dr. Hume. 
It will be observed that there is in this zone a sudden increase 
in the amount of fine clay. This increase is most marked near the 
extreme south-west and north-east points of the area we are de¬ 
scribing. At Swanage, Dorset, the amount of fine residue is 37 * 06 
per cent.; at Cerne Abbas, Dorset, 30*33 per cent., or 20 per cent, 
more than that at the top of the underlying zone ; at South Cave, 
Yorkshire, the increase is from 2 per cent, in the zone of H. sub- 
ylobosus to 30'33 per cent, in this zone. There is, however, no 
corresponding increase of the coarser inorganic material. 
4219 . 
Y 
