The Secondary Island.
The most cursory observation of the surface of the earth shows that it is composed of distinct substances, such as clay, chalk, lias, limestone, coal, slate, sandstone, &c.; and a study of such substances, their relative position and contents, has led to the conviction that these external parts of the earth have acquired their present condition gradually, under a variety of circumstances, and at successive periods, during which many races of animated beings, distinct both from those of other periods and from those now living, have successively peopled the land and the waters; the remains of these creatures being found buried in many of the layers or masses of mineral substances, forming the crust of the earth.
The object of the Islands in the Geological Lake is to demonstrate the order of succession, or superposition, of these layers or strata, and to exhibit, restored in form and bulk, as when they lived, the most remarkable and characteristic of the extinct animals and plants of each stratum.
The series of mineral substances and strata represented in the smaller island have been called by geologists “secondary formations,” because they lie between an older series termed “primary,” and a newer series termed “tertiary:” the term “formation” meaning any assemblage of rocks or layers which have some character in common, whether of origin, age, or composition.[1]
Following the secondary formations as they descend in the earth, or succeed each other from above downwards, and as they are shown, obliquely tilted up out of their original level position from left to right, in the Secondary Island, they consist: 1st, of the Chalk or Cretaceous group; 2nd, the Wealden; 3rd, the Oolite; 4th, the Lias; and 5th, the New Red Sandstone.