50 DISTRIBUTION OF MINERAL BEDS. 
large as to make it difficult to trace and mark the boundaries of 
each stratum, and compare its remote parts, with reference, either 
to their composition or to their imbedded organic remains. The 
extent, thickness, and composition of these strata have been in- 
vestigated by able geologists. The names they bear, are in part, 
such as having been first applied to them by miners or the inhabi- 
tants of the districts through which they pass, have since been 
adopted by the men of science devoted to these studies. 
Beginning with the uppermost and omitting some sub-divisions, 
there are the crag, London-clay, plastic-clay and sand, upper- 
chalk, lower-chalk, chalk-marl, green-sand, weald-clay, iron- 
sand, Portland limestone, Kimmeridge-clay, coral rag, calcareous 
grit, Oxford or clunch-clay, cornbrash and forest marble, great 
oolite, inferior oolite, lias, new-red-sandstone, magnesian lime- 
stone, the coal measures, millstone grit and shale, carbonife- 
rous or mountain limestone, old-red-sandstone. 
This long catalogue of uncouth names, shows at least, the 
minute accuracy with which the whole subject has been studied, 
and the extent to which the division of the strata has been car- 
ried. If we pass over to the continent of Europe, and compare 
the geological structure of France, the Netherlands, and Ger- 
many, with that of England, we find a general correspondence, 
but with important points of difference. Some formations are 
persistent, retaining the same characters over large tracts ; others 
are widely distributed, but liable to vary. What is a body of 
loose sand, or a soft and friable sandstone in England, (green- 
sand) in the Alps of Savoy, becomes a hard, blackish, compact 
limestone, proved to belong to the same epoch with the other, 
only by the circumstance of their containing imbedded in them 
the same organic remains. Some strata are confined within nar- 
row limits, to a single county, province, or department; or to a 
part of it, and in their place, there come in amongst those of the 
adjacent regions, one, two, three, or more equivalent formations 
as they are called, of which, their geological position shews that 
they are of nearly the same age, but which bear little resemblance 
to each other in any particular. The characters of these deposits 
are such, as to admit of their being distributed into a few families 
or groups, according to the following plan, where the corres- 
ponding strata of England, France, and Germany are ranged 
opposite to each other in parallel columns. 
Tertiary C^ ra S' 
svstem j London Clay, Strata of the Paris Strata of the Ba- 
y ' C Plastic Clay & Sand. Basin. sin of Vienna. 
Cretaceous 
("Chalk, Craie, 
I CI 
Chalk Marl, Craie Tufan, Kreide, 
'v^tem' 10 "v Green Sand, Glauconie Crayeuse, Planerkalk. 
' y ' J Weald Clay, Glauconie Sableuse. 
Uron Sand. 
