Geol. Mag. 1892. 



Dec. III. Vol. IX. PI. IV. 



Fig. 1. — Section of Hirnant Limestone x 20. 



The grains are made up of four layers— (1) Central nucleus of calcite. 

 (•2) Carbon. (3) " Chalcedonic " silica. (4) Outer bands of dusty 

 material and carbon. (3) and (4) are sometimes repeated. 



Fig. 2. — Section of Hirnant Limestone x 100. 



To illustrate Mr. L. W. Fulcher's paper on the Composition and Structure 

 of the Hirnant Limestone. 

 (p. 114.) 



