Vol. 59.] THE ASHBOURNE AND BUXTON RAILWAY. 345 



(5) The fine-grained limestones (1095, 1049, & 1073) 

 consist mainly of more or less crystalline calcite, which contains 

 small circular bodies (probably Ccdcisphcera), foraminifera, small 

 fragments of shells, encrinite-stems, lath-shaped prisms of calcite 

 with jagged edges, and a few quartz-prisms. 



(c) Granular or Oolitic Limestones. 



Several thin slices of the granular limestone from the Cold-Eaton 

 cutting, and one from the Heathcote cutting, were examined. 



Nos. 953 & 1074 were taken from the limestone a few inches 

 above the fifth clay in the Cold-Eaton cutting (see p. 342). Ex- 

 amined with a lens in a hand-specimen, the rock is seen to consist of 

 small grains and to contain small pebbles of limestone. Under the 

 microscope, it consists of oolitic grains and pellets and well-worn 

 pieces of limestone in a cement of calcite. 



The oolitic grains possess a concentric, and sometimes a radial 

 structure. In a few cases they show a black cross in polarized 

 light, but the majority consist of a brown non-crystalline substance. 

 They are generally circular or oval in section, and the nucleus 

 often consists of a foraminifer or a shell-fragment. (See PI. XXIII, 



fig- 1.) 



The pellets are amorphous, and possess no recognizable structure. 

 A few of them contain iron-oxide, and polarize in a grey tint. A 

 similar substance forms the nucleus of one of the oolitic grains, and 

 is very much like that of which the clay in thin slice 1075 is 

 composed. Some of the pellets probably represent small portions 

 of rolled clay, which have been incorporated in the limestone 

 immediately above it. 



The limestone-pebbles are well rounded, and contain foraminifera, 

 fossil-fragments, and sometimes oolitic grains. They are often 

 coated with a dark-brown amorphous substance, which is darker 

 than the interior of the pebble. There is no doubt that they have 

 been derived from a previously-consolidated limestone, and owe 

 their well-rounded form to attrition. The oolitic grains, pellets, 

 and pebbles are seldom in contact, but are cemented together by 

 crystalline calcite. (See PI. XXIII, fig. 2.) 



No. 1076, below the sixth clay-bed in the Cold-Eaton cutting, 

 and No. 969, below the second clay-bed in the Heathcote cutting, 

 have a structure similar to the preceding, but are not in so fresh 

 a condition. The majority of the oolitic grains either have been 

 altered to a dark substance, or originally contained less calcium- 

 carbonate. Amorphous pellets without any recognizable structure 

 are present. The cemen ting-material is crystalline calcite. 



The limestone above the fourth clay in the Cold-Eaton cutting is 

 oolitic, but some feet higher in the series it loses its granular 

 structure, and consists of shell-fragments, encrinite-stems, corals, 

 and foraminifera (954). 



