10 Messrs. W. Phillips aud Kent on [Jan. 



The slate which most nearly approaches that of Wales in 

 colour and general characters is found in a small quarry at the 

 eastern extremity of Woodhouse Eaves, but it is not so fine, and 

 is less fissile. The still coarser varieties of the several quarries 

 near Swithland are preferred as roofing slates, though rarely less 

 than one-fourth of an inch in thickness, and frequently varying 

 to half an inch, being of unequal thickness throughout, with a 

 surface often undulating, though ' at odd times,' as the quarry- 

 men expressed it, they are reduced to one-eighth of an inch. 

 These slates are split by the workman while in a standing posi- 

 tion, the slafe being supported by one band covered by leather, 

 and also by the arm ; while it is struck on the upper end by the 

 other hand, with the edge of a sharp instrument, in form resem- 

 bling a cooper's adze. The general hue of these slatf.s is green- 

 ish, and they readily yield to the knife a greyish powder, a cir- 

 cumstance inducing the conclusion of their softness ; while, on 

 the other hand, their edges cut window glass freely, showing 

 them to be compounded of at least two substances differing 

 greatly in respect of hardness. The reapplication of the point 

 of the knife along the surface gently, and with the knife loosely 

 held by the hand, indicates the passing of the point from one 

 hard substance to another through a softer, the line of section 

 becoming consequently irregular. The thin edges of the slate 

 are translucent, when very thin approaching to transparent in 

 spots ; and by transmitted light it becomes evident, that the 

 greenish hue of the slate is derived from the presence of a mul- 

 titude of specks of a blackish-green colour, which we consider 

 to be chlorite, because veins of that substance are frequently seen 

 traversing the slates in connexion with opaque quartz. The 

 muriatic acid has no perceptible action on these slates ; and we 

 conceive them to consist of a granular quartz, and of chlorite, 

 imbedded in another mineral which is considerably soft : this 

 we believe to consist of silex and alumine, in a schistose form, 

 thus imparting its slaty character to the rock. On examining 

 these slates with a very powerful glass on 'the fractured edges at 

 right angles to the plane of cleavage, minute and brilliant sur- 

 faces are perceived which have the aspect of transparent quartz. 

 A vein of yellowish talc inclosing grains of quartz traverses the 

 quarry at the extremity of Woodhouse Eaves. 



We have been the more particular in describing this slate, 

 which is the prevailing one of the country, from the belief that 

 all the varieties assumed by the rjcks of this tract, are consti- 

 tuted of the same materials, differing in their several proportions 

 and state of aggregation ; of course we do not include the foreign 

 substances imbedded in some of the varieties, and which occa- 

 sionally have the appearance of fragments, though we cannot 

 doubt from the composition and character, that some of the 

 included masses are of contemporaneous formation with the 

 rock itself. Hence it becomes requisite to give some account of 



