But they came at last, to a sea long past, And as they reach'd its shore, The Almighty's breath spake out in death, And the Ammonite liv'd no more. And the Nautilus now, in its shelly prow, As o'er the deep it strays, Still seems to seek, in bay and creek, Its companion of other days. And thus do we, in life's stormy sea, As we roam from shore to shore; While tempest-tost, seek the lov'd--the lost-- But find them on earth no more! Geology, in the magnitude and sublimity of the objects of which it treats, ranks next to Astronomy in the scale of the sciences. Sir J. F. W. Herschel. [Illustration] SUPPLEMENTARY NOTES. Note I. Page 13. _Shells in Chalk._ The shells of mollusca, in consequence of their durability, are the most abundant fossils in the sedimentary strata;[X] entire layers of marble and other limestone, of great thickness and extent, are wholly composed of an aggregation of a few species or genera: in some instances of fresh-water snails--as, for example, the Sussex and Purbeck marbles;[Y] in others, of marine bivalves and univalves, as the oyster-conglomerate of Bromley, and the shelly limestones of Portland, Dorsetshire, &c. [X] For an account of the geological value of fossil shells, see '_Medals of Creation_,' vol. i. p. 363. [Y] See '_Wonders of Geology_,' 6th Edition, p. 402. The cretaceous strata contain many hundred species of bivalves and univalves, by far the greater part of which belong to extinct genera; and the species, with but four or five exceptions, are unknown in more recent deposits. In loose sandy strata, fossil shells are oftentimes beautifully preserved, and may be obtained in as perfect a condition as if gathered from the sands on the sea-shores: such is the state of the specimens which abound in the sandy clays near Barton in Hampshire, and in the "_Crag_" of Essex and Suffolk. In certain beds of clay, shells are also found entire; sometimes retaining the epidermis, and the cartilaginous ligament of the hinge. The bivalves in the white chalk are generally perfect; but the univalves, probably from the more delicate structure of the originals, seldom retain any vestiges of the shell, excepting portions of the internal nacreous coat adhering to the chalk casts, which have been moulded in the interior of the shells. [Illustration: Lign. 19:--Bivalve shells (_Terebratulæ_) from Chalk (_natural size_). 1, 2. Plicated species. 1. _T. octoplicata._ 2. _T. subplicata._ 3, 4. Smooth species. 3. _T. semiglobosa._ 4. _T. subrotunda._ ] [Sidenote: TEREBRATULÆ FROM CHALK.]