After describing the one-sided tail of the more ancient fish, especially the fish of the Old Red Sandstone,--the subjects of his illustration at the time,--he stated, as the result of a recent discovery, that the young of the salmon in their fœtal state exhibit the same unequally-sided condition of tail which characterizes those existences of the earlier ages of the world. The individual fish, just as it begins to exist, presents the identical appearances which were exhibited by the order when the order began to exist. Is there nothing wonderful in analogies such as these--analogies that point through the embryos of the present time to the womb of Nature, big with its multitudinous forms of being? Are they charged with no such nice evidence as a Butler would delight to contemplate, regarding that unique _style_ of Deity, if I may so express myself, which runs through all his works, whether we consider him as God of Nature, or Author of Revelation? In this style of type and symbol did He reveal himself of old to his chosen people; in this style of allegory and parable did He again address himself to them, when he sojourned among them on earth. The chemistry of the formation seems scarce inferior in interest to its zoology; but the chemist had still much to do for Geology, and the processes are but imperfectly known. There is no field in which more laurels await the philosophical chemist than the geological one. I have said that all the calcareous nodules of the ichthyolite beds seem to have had originally their nucleus of organic matter. In nine cases out of ten the organism can be distinctly traced; and in the tenth there is almost always something to indicate where it lay--an elliptical patch of black, or an oblong spot, from which the prevailing color of the stone has been discharged, and a lighter hue substituted. Is the reader acquainted with Mr. Pepys's accidental experiment, as related by Mr. Lyell, and recorded in the first volume of the _Geological Transactions?_ It affords an interesting proof that animal matter, in a state of putrefaction, proves a powerful agent in the decomposition of mineral substances held in solution, and of their consequent precipitation. An earthen pitcher, containing several quarts of sulphate of iron, had been suffered to remain undisturbed and unexamined in a corner of Mr. Pepys's laboratory for about a twelvemonth. Some luckless mice had meanwhile fallen into it, and been drowned; and when it at length came to be examined, an oily scum, and a yellow, sulphureous powder, mixed with hairs, were seen floating on the top, and the bones of the mice discovered lying at the bottom; and it was found, that over the decaying bodies the mineral components of the fluid had been separated and precipitated in a dark-colored sediment, consisting of grains of pyrites and of sulphur, of copperas in its green and crystalline form, and of black oxide of iron. The animal and mineral matters had mutually acted