81 () THE PICTOU CUAL FIELD — POOLK. 



feet, and tlie total thickness of black shales over the mani seam- 

 under 2000 feet. 



McLeilann Brooh Section : — The rocks of this section overly 

 in regular seciuence the Albion measures which are intersected by 

 the Foord pit sinking-. The brook yields a continuous exposure 

 of the same series of shales, which vary in colour from light, 

 grey to black. They extend up to Black's mill site at A. 

 Walker's, wdiere they are succeeded by grey shales and the sand- 

 stone series that predominate in the higher beds. On page 241 

 of this paper the thickness of the mass of black shales over the 

 Main seam was taken from Logan at 1740 feet, but a recomputa- 

 tion would put it at less, or about 1520 feet. An extension of the 

 horizon of these shales finds sandstones substituted both to tlie 

 north and south ; this replacement is elsewdiere referred to. In 

 many pxrts the shales contain bands and nodules of clay iron- 

 stone, but seggregated and unworkable. The blacker shales are 

 of great thickness, some are compact, break with a cubical frac- 

 ture, and might be classed as inferior C'annel coals. They give 

 a black streak. Some were dug as " oil coals" in 1860, but the 

 demand for oil-bearing shales which then sprang up quickly 

 ceased w^ith the enormous development of the oil w^ells in Penn- 

 sylvania. Analyses of these shales on Marsh brook and on Mc- 

 Lellan's broolc at Patrick's pit are given in the Survey report of 

 Ls69, page 394. The samples are somewhat richer in volatile 

 matter than one casually selected from the shales of the Albion 

 measures which yielded Mr. Smaill of the Londonderry Iron Co 



Volatile matter , . 27,50 



Fixed carbon 6.50 



Ash 66.00 



100.00 



In all the amount of fixed carbon is low. 



Several of the more compact beds of black shale are of many 

 feet in thickness and furnish striking lines for tracing out the 

 structure of the section. The one at the mouth of Shale brook 

 shews the curve which the strata take on approaching the anti- 

 cline at Black's mill site. Generally on McLellan's brook the 



