27 
DEPOSITED IN WATER. 
This gritstone corresponds to the lower grits of Greenhow, and 
the ‘ bearing’ grits of Grassington ; and is a rock of much geological 
interest, as affording a term of reference where one was much needed. 
PASSAGE FROM THE SOUTHERN TO THE NORTHERN TYPE. 
The essential difference between these contrasted types is caused 
by the interpolation of sedimentary rocks between the limestone beds 
in all the northern tracts, which hence exhibit a complication of system, 
a repeated intermixture and succession of the four substances, (limestone, 
gritstone, shale, and coal,) which form in Bolland and Derbyshire only 
one succession. * 
The method of variation from one of these types to the other, — a 
very important subject of examination, — can be best studied in the 
neighbourhood of Great Whernside. 
The relations of the limestone series, at Grassington, and Greenhow 
Hill, and in Nidderdale, must be first studied. 
* Such are usually described in geology as simple and compound series of rocks : but a more 
exact nomenclature may be conveniently applied. In the southern tracts the same substances 
occur as in the northern ; but the combinations of them are many times repeated and varied. 
Now, as all words intended to characterize phenomena by reference to nature and number, may be 
formed upon algebraic analogy, we may consider the substances, as quantities, the definite combina- 
tions of these substances as terms, and any succession of these terms as a series of one, two, three, 
&c. terms. Hence arises the following nomenclature. 
Monomeric series. — When the substances occur only once, or in one compound term, as 
L + S + C. 
Di-tri and Poly-meric series. — When such terms occur twice, thrice, or many times. 
Homo-meric series. — When the successive terms are similarly composed. 
Hetero-meric series. — When these are not similarly composed, as ( L + S + C) + ( S + L + C) 
+ fC + S+Z.J 
Mono-di-tri-poly-nomial terms. — Applied to the number of substances in a term. 
Thus the Bolland rocks consist of gritstone, shale, and limestone in one succession. They con- 
stitute a trinomial term or monomeric series, and may be thus expressed, (G + A + L.j 
The Yoredale rocks consist of gritstone, shale, limestone, gritstone, coal, shale, limestone, shale, 
limestone, in many repetitions. They constitute a hetero-polymeric series. 
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