liiKOLOGY OP DERBYSHIRE. 225 



in certain directions. The shale commonly contains more or less 

 ironstone, which either lies in it in regular beds, a few inches or a 

 foot in thickness, or occurs in layers of balls or nodules, formed by 

 the aggregation of the mineral particles, not unfrequently round a 

 leaf or other organic body. These balls are frequently septarian, or 

 traversed by cracks which have been filled up by spar, generally of 

 carbonate of lime. The gritstones of the coal measures are gene- 

 rally a fine-grained sandstone, sometimes thick bedded, sometimes 

 splitting into large flags with beautifully smooth surfaces. These 

 gritstones vary much in hardness and quality, being sometimes a 

 food freestone, sometimes a hard stone with a ragged fracture, 

 (called cank), only fit for mending roads, and sometimes they pass 

 insensibly into shale and decompose rapidly by the action of the 

 atmosphere. The gritstones frequently form continuous masses 60 

 or 80 feet in thickness. The joints of the gritstone vary with the 

 character of the stone, being most regular in that which is thin bed- 

 ded and fine grained. The different coal seams of Derbyshire, not 

 only vary greatly in quaiity, but the same bed is frequently very 

 different in different parts of the country. They are sometimes hard 

 bright coals, being got in large blocks with smooth shining surfaces, 

 sometimes soft and crumbly, forming what are called caking coals. 

 From this great variety in the quality results the great advantage of 

 having coals in the district suited to all uses, from those calculated 

 for use in the drawing-room to others which are only fitted and are 

 best adapted for the furnace or the forge. The vertical divisional 

 planes of the coal beds in Derbyshire, which are there called slines, 

 and which nearly answer to the joints of other rocks, follow the 

 same remarkable law which they are found to do in other places, 

 and run about magnetic N. and S.* The number of workable coals 

 in Derbyshire is considerable, amounting to at least fifteen or six- 

 teen beds ; but for want of a general system of nomenclature, it is 

 very difficult to trace these across the country, or to identify them 

 in different localities, since the names given to the beds in one place 

 are unknown in another only a few miles distant. There are five 

 or six beds which are from four to six feet in thickness ; one seam 

 over the south part of the district is nine feet thick, but it is pro- 

 bably there composed of two beds; and there are many others 

 which vary in thickness from three or four feet to as many inches. 

 Each bed commonly preserves its thickness over a very wide area, 



• The miners are often fully aware of this universality in the direction of 

 what is called, in different places, the sline ; for, in answer to my question, 

 one of the workmen told me that the cleet or the face of the coal " faced two 

 o'clock sun, like as it does all over the world as I ever heard on." 



VOL. VIII., NO. XXIV. 29 



