286 RAMBLES OF A GEOLOGIST. 



lay at right angles with the fibres of the others in immediate 

 contact with it. In the inner table of one scale I reckon 

 nine of these alternating, variously-disposed layers ; so that 

 any application of violence, which, in the language of the 

 lath-splitter, would run lengthwise along the grain of four of 

 them, would be checked by the cross grain in five. In other 

 words, the line of the tear in five of the layers was ranged 

 at right angles with the line of the tear in four. There were 

 thus in a single scale, in order to secure the greatest possible 

 amount of strength, and who can say what other purposes 

 may have been secured besides 1 three distinct principles 

 embodied, the principle of the two tables and diploe of the 

 human skull, the principle of the variously arranged coats 

 of the human stomach, and the principle of Oliver Crom- 

 well's "fluted pot." There have been elaborate treatises 

 written on those ornate flooring-tiles of the classical and mid- 

 dle ages, that are occasionally dug up by the antiquary amid 

 monastic ruins, or on the sites of old Roman stations. But 

 did any of them ever tell a story half so instructive or so 

 strange as that told by the incalculably more ancient ganoid 

 tiles of the Palaeozoic and Secondary periods ? 



I called, on my way back from Linksfield, upon my old 

 friend Mr Patrick Duff, and was introduced once more to his 

 exquisite collection, with its unique ichthyolites of at least 

 two genera of fishes of the Old Red, the Stagonolepis and 

 Placothorax of Agassiz, which up to the present time are 

 to be seen nowhere else ; and various other fine specimens 

 of rare species, which, having sat for their portraits, have 

 their forms preserved in the great work of the naturalist of 

 Neufchatel. He showed me, with some triumph, one of his 

 later acquisitions, a fine specimen of Holoptychius from the 

 upper yellow sandstone of Bishop-Mill, which exhibits the 

 dorsal ridge covered with a line of large overlapping scales, 

 not at all unlike those overlapping plates which cover the 



