. The testimony of the rocks; . ing thegreatest possible amount of strength from the least possibleamount of thickness. The scales of Holoptychius giganteusmay be selected as representative of those of the family towhich it belonged. It consisted of three plates, or rather,like the human skull, of two sohd plates, with a diploe orspongy layer between. The outer surface was curiously fret-ted into alternate ridges and furrows; and hence the nameof the genus, — lorinkled scale ; and these imparted to theexterior plate on which they occurred, and which wasformed of solid bone, the strength which
. The testimony of the rocks; . ing thegreatest possible amount of strength from the least possibleamount of thickness. The scales of Holoptychius giganteusmay be selected as representative of those of the family towhich it belonged. It consisted of three plates, or rather,like the human skull, of two sohd plates, with a diploe orspongy layer between. The outer surface was curiously fret-ted into alternate ridges and furrows; and hence the nameof the genus, — lorinkled scale ; and these imparted to theexterior plate on which they occurred, and which wasformed of solid bone, the strength which results from a cor-rugated or fluted surface. Cromwell, in commissioning afriend to send him a helmet, shrewdly stipulated that itshould be a fluted pot; and we find that the Holoptychiushad got the principle of the fluted pot exemplified in theouter plate of each of its scales, untold ages before. Thespongy middle plate must, like the diploe of the skull, haveserved to deaden ths vibrations of a blow dealt from the Fig. SECTION OF SCALE OF HOLOPTYCHIUS. (Mag. eight diameters.) outside. It was a stratum of sand bags piled up in the mid-dle of a plank rampart. Their innermost table was formed,like the outer, of solid bone, but had a diflerent arrange-ment. It was properly not one, but several tables, in each ON THE TWO THEOLOGIES. 249 of which the osseous fibres, spread out in the general planeof the scale, lay at a diverse angle from those of the tableimmediately in contact ^Wth it. The principle was evidentlythat of the double-woven cloth, or cloth of two incorporatedlayers, such as moleskin^ in which, from the arrangementof the threads, what a draper would term the tear of theone layer or fold lies at a different angle in the generalfabric from that of the other. We are thus presented, in asingle fossil scale little more than the eighth part of an inchin thickness, TVith three distinct strengthening principles,—the principle of Cromwells fluted pot,—the principle
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