19

Mr. Farey®, on the other hand, consi-ders the wedge-like form a distinctive cha-racter of alluvial matters; these, he tellsus, never appear stratified in the uniformmanner peculiar to regular strata, but thebeds, when sunk through, frequently featherout, or are wedge-like, and intermix witheach other.

Where the same property is representedas characteristic of substances so different,the presumption is that it will not be foundcharacteristic of any.

In the Memoir of Cuvier b and Brong-niart on the environs of Paris, it is stated,that before the later formations, mentionedin that memoir, were deposited, the chalkupon which they rest must have presenteda surface varied with depressions and pro-tuberances. These inequalities are clearlyascertained by the islands and promontoriesof chalk which occasionally penetrate the

1 Farey’s Survey of Derbyshire p. 131. See also hisRemarks on the Stratification of France and England,in Philosophical Magazine.

b Recherches sur les Ossemens Fossiles, tom. i. p. ) 1and 15.

c 2