Mr. 
Farey’s Notes on Mr. Bakewell’s Geology. 365 
-P,138, the central parts of Europe, mentioned in your 
a 
139, |. 
xxxvith vol. p. 442. The Wilicksa salt strata, 
seem also to me, to agree with those of Paris, 
Kir. Geo. Ess. p. 873. 
6, in Northumberland*.—* In Birtley Colliery 
in Durham, about the year 1785, a Salt spring 
was cut, at 140 yards beneath the surface, from 
whence, for some years past, 1100 tons of Salt 
have been made annually, see Mr. Bailey’s Report 
47 
1.8, under the surface *, —* The Spring here al- 
Juded to, is in the Warren-hill Colliery (Rep. i. 
213), and besides issuing so much below the level 
of the Sea, it contains one half more salt, in a 
given weight of water; its produce being -/;th of 
salt, and that of the sea J;th, according to Kir- 
wan. The situation of this salt Spring, is I be- 
lieve, near to the great Fault which surrounds the 
Ashby-de-la-Zouch Coal-field ; beyond which (in 
the Red Marl, as [ understand) 2m. W of Donis- 
thorp, on the N side of the foot-path to Overseal, 
is a Spring on the surface, in Sir Francis Burdett’s 
Estate, nearly as Salt as that above mentioned, 
and as another Spring which oozes into Donis- 
thorp Colliery (Rep. i. 196 and 503), accom- 
panied by hydrogen gas and a hissing noise, above 
80 yards beneath the surface; but in which last 
Pit, it soon becomes mixed with fresh water 
from nearer the surface, and appears less salt, 
than in Warren-hill Pit. 
6 and 7, never found upon it *.—* This is not 
literally true, even of the Ist Grit Rock or proper 
“¢ Mill-stone Grit” of Mr. Whitehurst, because 
of the perfect though very thin Coals, in the 
Limestone Shale, Rep. i. 234; and the 3d Grit 
Rock, often proves even coarser-grained than the 
Ist, and was mistaken for it by Mr. Whitehurst, 
in Chatsworth old Park (as I have shown, Rep. i. 
178) where three Coal-seams underlie his mill- 
stone Grit ! 
A not less striking proof of the impropriety of 
this hasty generalization by Mr. W. and repeated 
by Mr. B. occurs on the Green and Tinkers-knowl 
Commons in Tansley ; these being near to the line 
of Mr. Whitehurst’s Section in Plate LV, of his 1st 
Edition, where the 1st Coal has long been occa- 
. sionally 
