COAL MEASURES. 



93 



tninks that the thickness of the strata may fairly be 

 estimated at 2500 feet. 



In Newcastle, England, the coal alternates with 

 the rock measures 32 times. Thus : sandstone, 24 

 yards ; coal, six inches ; rocks, 10 yards ; coal, eight 

 inches; rocks, 22 yards ; coal, six inches ; rocks, 15 

 yards ; coal, one foot ; and so on, till we have 380 

 yards of rock and 15 yards of coal, with 32 alterna- 

 tions ; there being 32 beds of coal, 62 of sandstone, 

 17 of limestone, one of trap, and 128 of beds of shale 

 and clay. 



Mr. Bakewell has deduced the following results 

 from a large number of facts and observations in 

 relation to the coal formation of England : 



1. The series of strata called, collectively, the 

 great coal formation, commonly rests upon or covers 

 marine strata, chiefly the upper transition or mount- 

 ain limestone. 



2. The coal strata, to a vast depth, contain exclu- 

 sively the remains of terrestrial or of fresh-water 

 plants or minerals ; hence it may be inferred that 

 such strata are of fresh-water formation, though 

 some of the lower beds in certain districts contain 

 occasionally an intermixture of marine shells. 



3. The coal strata appear generally to have been 

 deposited in tranquil water ; a few beds only pre- 

 sent indications of having been transported from 

 a distance by violent currents. 



4. The coal strata, after their deposition in inland 

 lakes or estuaries, subsided and were submerged in 

 the ocean, and were covered in many parts by ma- 

 rine strata, particularly the magnesian. 



5. The faults that dislocate the coal strata were, 

 in some instances, formed before the deposition 

 of the upper marine strata ; other faults were form- 

 ed at a subsequent epoch, after the deposition of 

 the marine strata ; but in both cases it may be in- 

 ferred that the strata were beneath the sea when 

 the dislocation by faults took place. 



