346 MR. H. H. AENOLD-BEMEOSE ON THE GEOLOGY OF [Aug. 1903, 



(d) Encrinital Limestone. 



Limestones with portions of encrinite-stems are common in the 

 cuttings. They may be easily identified in hand-specimens, and in 

 thin slices show the usual sections of these fossils. 



(e) Clay-Parting. 



(1075) A specimen of the soft clay from clay-parting No. 5, in the 

 Cold-Eaton cutting (see p. 342), was kept in a drawer for several 

 months. It was then sufficiently hard and dry for a thin slice to 

 be made from it. Under the microscope it was seen to be amor- 

 phous, and contained iron-oxide. There were present a few needle- 

 shaped crystals and prisms, with parallel extinction and positive 

 double-refraction, polarizing in grey tints : these may be referred 

 to quartz. Another small prism polarized in a yellowish-red, stood 

 out in relief, had positive double-refraction, and may be assigned 

 to zircon. 



EXPLANATION OF PLATES XXII & XXIII. 



Plate XXII. 



Fig. 1. Anticline and syncline in Mountain-Limestone, Alsop-en-le-Dale Cut ting, 

 London & North- Western Railway. (See p. 341.) 

 2. Anticline in Mountain-Limestone, same locality. (See p. 341.) 



Plate XXIII. 



Fig. 1. Oolitic and pebbly limestone, x50, resting on the fifth clay-bed, Cold- 

 Eaton Cutting, London & North-Western Railway. The oolitic grains 

 show radial, and sometimes concentric structure. They are rarely in 

 contact, and are separated by calcite, more or less crystalline, which 

 exhibits very little structure or detail under the microscope (953). 

 (See p. 345.) 

 2. Oolitic and pebbly limestone, X 25, resting on the fifth clay-bed, same 

 locality. The figure contains a pebble of fossiliferous limestone and 

 small pellets (1074). (See p. 345.) 



Discussion. 



The Chaieman (Mr. Teall) said that he was much pleased to 

 know that the Author was continuing his excellent geological work 

 in Derbyshire. In regard to the oolitic structures mentioned, he 

 cited a paper recently published in the Neues Jahrbuch, where the 

 results of an examination of recent oolitic grains showed that they 

 were formed of aragonite, and so the inference had been drawn 

 that all oolitic grains were aragonite to start with, and that the 

 change to calcite had taken place in the process of fossilization. 

 Moreover, it was found that if calcium-carbonate was precipitated 

 from sea-water by the action of ammonium-carbonate on the calcium- 

 sulphate spherules of aragonite were formed. 



Prof. Sollas enquired whether the Author had discovered traces 



