or perforated cave-rock. A winding path, however, meets this part of the road, by which there is an easy ascent to the upper cave. A new road is also now forming by Mr Lloyd, with great taste and judgment, along the side of the cliff, near to which, and at no great distance above it, and about half a mile from the upper cave, another excavation in the rock presents itself, which, on examination, I found to be entirely blocked up with soil, and has clearly never been open to human observation. But I have no doubt, from its appearance and character, that it will prove closely analogous to this which has been the subject of the present communication, and will therefore, there is every reason to believe, exhibit as rich a prospect, whenever its recesses may be explored, in search of those organic remains of animals now unknown in the temperate zɔnes. These roads and the situation of the caves shewn in Fig. 1. of Plate I. On the Silicification of Organic Bodies *. With a Plate. By Baron LEOPOLD VON BUCH. FROM the lively intercourse of naturalists with one another, it has happened that a number of minute observations have become far spread and well known, before any public mention has been made of them. Every communication of such observations, when made by persons of ability, will assume another form. Either one has to add other facts to those originally discovered, or knows how to place these same under other points of view; and thus give a new, more comprehensive, and detailed account of them, from the observations which they suggested. Then it is often difficult, perhaps impossible, to trace back to their origin the individual facts and observations, which at length afford rich and fruitful results. The priority as to the original discovery becomes lost, the more easily, that in general it cannot be at all foreseen what may arise out of an apparently trifling discovery in other hands, or whither it may lead. But true naturalists have never cared much about priority of discovery such a feeling would disturb every sort of fellowship. It would be easy to imagine that the germ of important discoveries : * Read in the Academy of Sciences (of Berlin) upon the 28th of February 1828, and translated from the German original by George F. Hay, Esq. and views lay in some indefinite superficial view, or in loose facts, which were only thrown together as mere conjectures. This personal communication, if we may say so, has, however, the disadvantage, that remarkable facts and reflections worthy of remark, have become for long a kind of common good; and notwithstanding this, the observations or discoveries have not reached those who might have made them the means of effecting the greatest benefit to science. And many facts, many views, are entirely lost, because their authors did not deem them worthy of being made public; or those who may bring them forward, are unable to apply them to more extended views. The object with which I wish to engage the attention of the Academy for a short time, viz. The Silicification of organic bodies, is of the above class. The remarkable appearance is known to many, but with very different degrees of accuracy. Many excellent naturalists indeed are ignorant of its existence, notwithstanding that it is daily before their eyes, because no publication has directed their attention to it. The greatest share in the discovery of remarkable facts on this topic, appears in the mean time to belong to M. Brogniart of Paris, who some time since prepared a work on this subject. Some illustrations from the above work have been published in pl. 6 and 7 of the engravings in the Dictionnaire d'Histoire Naturelle*. He who occupies himself with the study of fossils, knows very well how many shells are completely converted into flint and calcedony; and that, since the soft parts of the animals do not remain, only the harder calcareous shell, the whole silicifying process must have developed itself upon this hard shell. Many univalve shells are found in their spiral form, composed of the most beautiful calcedony. Many corals appear as jasper or quartz. It is known that it has been long wished to prove from this appearance, that chalk changes into a siliceous substance, and carbonate of lime into • The author states, that in J. Sowerby's Min. Conch. vol. iv, plate 330), (year 1823), there occurs the following remarkable passage: "Productus latissimus from Anglesea. In chertz (mountain) limestone, the shell is in many parts gone, and its place supplied by silex in numerous small drops, each surrounded by several irregular rings of the same material, a form of silex not rare among fossil remains of shells, composed of laminæ strongly impregnated with gluten, as Ostrea, Pectens, &c. in the green sand and other formations." Page 44. |