54 M. Von Buch an the Silicificatwn of Organic Bodies. 



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 wordiy 

 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 bo- 

 dies^ is of the above class. The remarkable appearance is known to 

 many, but with very different degrees of accuracy. Many excel- 

 lent naturalists indeed are ignorant of its existence, notwithstand- 

 ing that it is daily before their eyes, because no publication has 

 directed their attention to it. The greatest share in the disco- 

 very of remarkable facts on this topic, appears in the mean time 

 to belong to M. Brogniart of Paris, who some time since pre- 

 pared a work on this subject. Some illustrations from the above 

 work have been published in pi. 6 and 7 of the engravings in 

 the Dictionnaire d'Histoire Naturelle*. He who occupies him- 

 self 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 la- 

 tissimus 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 laminae strongly 

 impregnated with gluten , as Ostrea, Pectens, &c. in the green sand and other 

 formations." Page 44. 



