Let us now examine the position and formation of the interior strata: the earth, says Woodward, appears in places that have been dug, composed of strata placed one on the other, as so many sediments which necessarily fell to the bottom of the water; the deepest strata are generally the thickest, and those above the thinnest, and so gradually lessening to the surface. We find sea shells, teeth, and bones of fish in these different beds, and not only in those that are soft, as chalk and clay, but even in those of hard stone, marble, &c. These marine productions are incorporated with the stone, and when separated from them, leave the impressions of the shells with the greatest exactness. "I have been most clearly and positively assured," says this author, "that in France, Flanders, Holland, Spain, Italy, Germany, Denmark, Norway, and Sweden, stone, and other terrestrial substances are disposed in strata, precisely the same as they are in England; that these strata are divided by parallel fissures; that there are inclosed within stones and other terrestrial and compact substances, a great quantity of shells and other productions of the sea, disposed in the same manner as in this island. I am also informed that these strata are found the same in Barbary, Egypt, Guinea, and in other parts of Africa; in Arabia, Syria, Persia, Malabar, China, and the rest of the provinces of Asia; in Jamaica, Barbadoes, Virginia, New-England, Brazil, and other parts of America[198:A]." This author does not say how he learnt, or by whom he was told, that the strata of Peru contained shells; yet as in general his observations are exact, I do not doubt but he was well informed; and am persuaded that shells may be found in the earth of Peru, as well as elsewhere. This remark is made from a doubt having been formed some time since on the subject, and which I shall hereafter consider. In a trench made at Amsterdam, to the depth of 230 feet, the strata were found as follows: 7 feet of vegetable earth, 9 of turf, 9 of soft clay, 8 of sand, 4 of earth, 10 of clay, 4 of earth, 10 of sand, then 2 feet of clay, 4 of white sand, 5 of dry earth, 1 of soft earth, 14 of sand, 8 of argil, mixed with earth; 4 of sand, mixed with shells; then clay 102 feet thick, and at last 31 feet of sand, at which depth they ceased digging[199:A].