In another magnified portion of the pebble, a specimen of the microscopic discoidal shells which we have already seen compose the greater part of the white chalk (_Lign. 5_, p. 14), is beautifully displayed when viewed by transmitted light, under a highly magnifying power (_Lign. 12_).[K] Our investigation has thus shown, that a great part of the pebble is actually composed of the aggregated fossil remains of animalcules, so minute as to elude our unassisted vision, but which the magic power of the microscope reveals to us, preserved, like flies in amber, in all their original sharpness of outline and delicacy of structure. [K] Note VI. _Rotaliæ in chalk and flint._ [Sidenote: ROTALIA IN FLINT.] [Illustration: Lign. 12:--Rotalia in flint: highly magnified.] On another fragment of this stone two glittering specks, not larger than a pin's head, are discernible (_Lign. 9_): these with a magnifier of moderate power, are seen at a glance to be scales of fishes. But they differ from each other; both have the surface smooth, and without enamel: in the one the margin or edge is simple (_fig. 3_); in the other, it is divided like the teeth of a comb (_fig. 2_);--trifling as this difference may appear, it is sufficient to enable the naturalist to determine that the fishes which furnished these scales belonged to two distinct orders, of which the Salmon and the Mullet are living examples. [Illustration: Lign. 13:--Scales of Fishes in flint. Fig. 1.--A fragment of the pebble with the scales of the natural size. 2.--One of the Scales (of a species of _Beryx_) highly magnified. 3.--The other Scale (of a species of _Salmo_). ] [Illustration: _Plate II._ _Longitudinal section of the Pebble._ _Page 41._] [Sidenote: SECTION OF THE PEBBLE.] SECTION OF THE PEBBLE. _Plate II._ We will now avail ourselves of the assistance of the lapidary, and divide the pebble in a longitudinal direction;--what a beautiful and interesting section is thus obtained! The markings observable on the fractured portion of the stone (see Plate I, c), are thus shown to have originated, as we surmised, from some organic body, which the flint, when fluid, had penetrated and enveloped. The enclosed fossil was obviously one of those soft marine zoophytes, allied to the _Actiniæ_ or _Sea-Anemones_, which are of a globular, spherical, or inversely conical shape, and consist of a tough, jelly-like substance, permeated with tubes, disposed in a radiated manner around a central cavity, or digestive sac; a structure admitting of that constant supply and circulation of sea-water, which the economy of these curious forms of animal existence requires. [Sidenote: ISLE OF WIGHT PEBBLES.]