W. S. Gresley — Bouklers in a Coal-seam. 555 



four out of five of these boulders were found within 80 or 90 yards from 

 the edge of a " horse " or '• wash-fault " of unusual width (100 yards), 

 their connection with this interruption in the coal may be very close. 



Of the several theories advanced respecting the way in which 

 boulders have become enveloped in Coal-beds, I am inclined to 

 accept that one which supposes that they have been dropped or 

 washed out of the roots of trees as they were floated along in flood- 

 time from higher ground on which they grew. And there seems 

 every reason to believe that as the matter composing the Midland 

 Coal-measures undoubtedly came from the N.W., the parent rock 

 from which these boulders have been derived existed more or less 

 in that direction. 



In conclusion it may be interesting to cite several other 

 authenticated instances of the occurrence of quartzite or other boulders 

 and pebbles, either embedded in seams of coal or in the " measures " 

 enclosing them. 



(a) In a collierj'- in Shropshire, a water-worn pebble of lead ore 

 was taken (by Mr. George Spencer, the manager) from the top of a 

 Coal-seam in the workings. [From this fact we learn that mineral 

 veins — of lead-ore at any rate — were formed prior to the deposition 

 of the Coal-measures.] 



(&.) At Church Gresley Colliery, in Derbyshire, at 630 feet deep, 

 in 18G7 was found a boulder composed of hard, crystalline sandstone, 

 dotted with small, angular quartz-pebbles, having a smooth, well- 

 worn surface; it measures ten inches in diameter by six inches thick, 

 and in this latter particular coi'responded exactly with the thickness 

 of the clay (the underclay of the "Little Coal" seam) in which it 

 reposed. Again, quite recently (1885) four or five little grey 

 quartzite pebbles, the largest being roughly the size of a hen's egg, 

 were obtained from the same stratum of underclay in the same pit ; 

 they were all near together. 



(c.) In North Staffordshire two instances of large rounded boulders 

 occurring in the Coal-measures are mentioned in the Eeport (for 

 1865) of the British Association. — See "Keports," p. 42. 



{d.) The South Wales Coal-field has yielded pebbles. See Memoir 

 of Geological Survey, vol. i. p. 194. 



(e.) In the Forest of Dean Coal-field. Mr. Buddie's account in 

 Trans. Geol. Soc, 2nd series, vol. vi. p. 217. 



(/.) The Lancashire Coal-districts, including Cheshire. Many 

 boulders have been discovered in working the mines, accounts of 

 which may be found in Memoirs of the Lit. and Phil. Soc. of Man- 

 chester, vol. ix. 2nd series, 1851 ; Trans, of the Manchester Geol. 

 Soc. vol. xiii. p. 141 ; also vol. xiv. p. 373. 



In America, in the Tennessee and Ohio Coal-fields quartzite boulders 

 have occurred more or less buried in Coal-seams. See Dana's 

 Manual of Geology, p. 317. 



