POPULAR GEOLOGY. 49 



some beds of stone there are large boulders, generally egg-sliaped, weigh- 

 ing many hundred pounds and sometimes as much as two or three tons. 

 They are surrounded by a mass of soft sand called mare ; and internally 

 they are generally composed of a very hard, dark crystalline substance, 

 very much like basalt or whinstone. How they came there is a mystery 

 which cannot easily be solved, but that they do occur in the midst of the 

 best stone beds is a fact which many quarry owners know to their cost. 



Though the Flagstone formation as a Avhole is pretty uniform and 

 constant in character, yet no two quarries are alike, or have exactly 

 the same group of beds, however near they may be to each other; and very 

 often the same quarry presents a difEerent appearance at its two extremities, 

 than it does at the other : but more especially is this the case in the above 

 quarries where the beds are so numerous. The beds of shale in this 

 formation, as in all others, are the most regular and extend over the 

 greatest area and yet even they vary very much. There is a bed of shale 

 (No. 2 in section 1.) which is only six inches thick in the quarry fi'om 

 which section 1 was taken, in the next quarry about 200 yards to the 

 south it is nearly ten feet thick, and. in an old quarry about the same 

 distance to the north it is five feet thick. It extends right across Swale's 

 moor with an average thickness of about four feet. The next bed of shale 

 (No. 4 in section 1.) is more regular. It extends almost over the whole of 

 Eingby and Swale's moor, varying in depth from three to four feet, but it 

 gradually thins out to the east, and it is absent altogether at the quarry from 

 which section 2 was taken. 



The beds of stone vary extremely both in thickness and quality. 

 While some beds remain pretty regular for a great distance, others will 

 begin at a point like the thin end of a wedge and gradually increase until 

 they becomes four or six feet or more in thickness, or a thick bed will some- 

 times rapidly thin out entirely in 10 or 20 yards. Such cases are of 

 frequent occurrence in these quarries. The base of this series consists of 

 a thick bed of ashlar stone varying from 7 feet to 16 feet in depth ; it 

 extends into Northowram where it forms thick beds of ashlar in some places 

 and in others thin bedded flagstones. The formation derives its name 

 from the vast quantity of flags which it annually yields. The industrial 

 importance of the Flagstone rock is very great. It gives employment in 

 our neighbourhood to thousands of persons, and adorns our town with 

 magnificent edifices and other monuments of man's industry and intelli- 

 gence which will endure for ages yet to come. Great quantities of the stone 



