Geology and Mineralogy: Considered with Reference to Natural Theology by William Buckland

Author:William Buckland [William Buckland]
Language: eng
Format: epub
Publisher: William Pickering
Published: 2018-05-17T16:00:00+00:00

OF THE 327

in the act of admitting or rejecting the pericardia l fluid.

The principle to which we thus refer the rising and sinking of the living Nautilus, has been already stated (P. 318) to be the same which regulates the ascent and descent of the Water Balloon: the forcing of a quantity of water into the single air chamber of the balloon compresses the air, and increases the quantity of matter in this chamber, without enlarging the magnitude of the bal in the colour of the spar. In both these fossil Nautilus, the entire series of the earthy casts within the represents the bulk of fluid which this pipe could hold.

The sections, PI. 32, Fig. 3, d. e. f., shew the edges of the calcareous sheath surrounding the oval casts of three compartments of the expanded This calcareous sheath may have been flexible, like that surrounding the membranous pipe of the recent Nautilus (PI. 31, Fig. 1, b. d. e.) The continuity of this sheath across the air chambers, (PI. 32, Fig. 2, d. e. f. Fig. 3, d. e. f. and PI. 33), shows that there was no communication for the passage of any fluid from the into these chambers: had any such existed, some portion of the fine earthy matter, which in these two fossils forms the casts of the must have passed through it into these chambers. Nothing has entered them, but pure crystallized spar, introduced by infiltration through the pores of the shell, after it had undergone sufficient decomposition to be percolated by water, holding in solution carbonate of lime.

The same argument applies to the solid casts of pure crystallized carbonate of lime, which have entirely filled the chambers of the specimen PI. 32, Fig. 1; and to all fossil Nautilus and Ammonites, in which the air chambers are either wholly void, or. partially, or entirely filled with pure crystallized carbonate of lime. (See PI. 42, Fig. 1, 2, 3, and PI. 36). In all such cases, it is clear that no communication existed, by which water could pass from the interior of the siphon to the air chambers. When loon, and thus increasing its specific gravity, causes it to sink; when the pressure is removed, the air within the chamber expands and expels the water, the specific gravity of the balloon is diminished, and it again rises.* I shall conclude this attempt to illustrate the structure and economy of fossil Nautilus by those of the living species, with shewing in what manner the chambers of the pearly Nautilus, supposing them to be permanently filled only with air, and the action of the supposing it to be the receptacle only of a fluid, interchanging its place alternately from the to the pericardium,\ would be subsidiary to the movements of the animal, both on the surface, and at the bottom of the sea.

First, The animal captured by Mr. Bennett, was seen floating at the surface, with the upper portion of the shell raised above the water and kept in a vertical position by means of the included air (see PL 31, Fig.

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