344 Mr. Witham on the Greenstone Dyke, Sfc. 



of the seam, which has been reduced to cinder. On each side of the dyke, 

 between it and the regular strata, there is a thin gut or core of clay, about 

 six inches thick, which turns the rain water on the rise side and forces it 

 to the surface, forming numerous springs as it traverses the country. 

 The coal spoiled by the action of this Greenstone Dyke is as follows : — 

 twenty-five yards of bad short coal, half reduced to cinder ; sixteen yards of 

 cinder, and ten yards of the sooty substance before described, making, toge- 

 ther, fifty yards. Should a similar effect have taken place on the rise side 

 of which (from what has already been wrought) no doubt can be entertained, 

 it will make altogether upwards of one hundred yards in breadth of coal, 

 which the effect produced by this dyke has rendered quite unfit for ordinary 

 colliery purposes. The dyke itself, at this point, is eighteen yards thick. 



Here, then, we have a most convincing proof that the substance ejected 

 into and through this immense crack, must have arrived at the surface in 

 a state of most intense heat, and which, when cooling, shrunk or contract- 

 ed, so as to produce on each side what is called the gut or core of 6 inches, 

 now filled with clay, as before observed. Water worn stones have occasion- 

 ally been found embedded in the solid coal of the main seam. 



The Greenstone of the dyke is of great value throughout the whole line 

 for making and repairing roads, for which purpose it is quarried in every di- 

 rection upon Cockfield Fell ; it has been used for the above purpose upwards 

 of seventy years, Mr. Dixon being the first person there who so applied it. 



I trust no apology can be necessary for stating facts of the above de- 

 scription, which must be of use to any one who may undertake to explain 

 the interesting phenomena of Whin Dykes. 



Whilst mentioning the Whin Dyke of Cockfield Fell, I must observe, 

 that there are here, as throughout the whole coal field, numerous faults, all 

 of which by the miners are called dykes ; these are, perhaps, more difficult 

 of explanation than the other, and as materially affecting the regular strati- 

 fication of the coal, are of more importance to the mine owner. These are 

 those cracks and slips which throw the coal and other strata out of their 

 regular bearing, either up or down. These cracks are generally not more 

 than five or six inches wide, and the substance contained in them is an in- 

 durated impervious clay. 



