Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 2.djvu/73

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The figures in this Plate are selected to exemplify some of the various manners in which the shells of Ammonites are adorned and strengthened by ribs, and flutings, and bosses. In Vol. I. p. 257, instances are mentioned of similar contrivances which are applied in Art to strengthen thin plates of metal. Workers in Glass have also adopted a similar expedient in their method of fortifying small wine flasks of thin glass, made flat, and portable in the pocket, with a series of spiral flutings passing obliquely across the sides of the flask, as in many of the flattened forms of Ammonite. Similar spiral flutings are introduced for the same purpose on the surface of thin glass pocket smelling bottles. In other glass flasks of the same kind which are made in Germany, the addition of bosses to the surfaces of the flat sides of the bottles, produces a similar double result of ornament and strength.

Air-chambers of Ammonites heterophyllus, filled with Lias, and showing in a remarkable degree the effect of the undulating course of the edges of the transverse plates beneath the flat sides of the outer shell.