UncrystalUzed Mineral Substances. ' 355 



- the operation to which they owe their present condition did not consist 

 of a composition and a substitution ; that it was not of a chemical na- 

 ture ; that it did npt take place slowly and in a continuous manner, but 

 that it was the calm and tranquil result of a mechanical deposition. It 

 may easily happen that we may accidentally notice, in a chemical opera- 

 tion, certain identical parts which have undergone no change notwith- 

 standing the alteration of the principal mass, just as we find unaltered 

 flour in the dough of bread, chalk in silex, or foreign substances imbedded 

 in crystals ; but heterogeneous portions, arranged in series of regular for- 

 mation, present a character peculiar to the configurations in question, in 

 which are formed, in a manner altogether remarkable and different from 

 what is usualh* observed, and under the influence of a particular force, 

 lapideous rings, free, concentric, and unconnected with each other ; be- 

 tween which alternate layers of lime with the animalcules of the chalk are 

 deposited, giving rise to forms having a solid nucleus with a free but solid 

 ring, suggesting to the fancy the figure of Saturn and his ring. 



From these researches it appears how important it is to examine with 

 more attention the inorganic forms which have long been known by the 

 name of clayey, marly, or calcareous kidneys, as well as those called 

 Imatra stones, which have often a well-determined shape, and have hi- 

 therto been considered, in the ingenious and exact classifications of cn*s- 

 tallography, as amorphous masses, and placed in books on mineralogy 

 among stones along with soft minerals of the same species, or in works 

 on geology according to their particular position, and their formation 

 ascribed to the general agency of attraction. It appears that an attempt 

 has likewise been made, but with little success, to ascribe to these pheno- 

 mena the formation of stalactites as well as that of oolites ; but Mr Sedg- 

 wick has sufficiently shewn, that the deposits of calcareous kidneys, so 

 common in the neighbourhood of Sunderland, were altogether foreign 

 to the formations of stalactites. Properly speaking, they are only forma- 

 tions resembling oligistic iron, stalactitic or mamellated. 



Viewing the matter in another light, some highly respectable mineral- 

 ogists have thought proper to form the crystalloids, into a group, which 

 they place beside crystals, and in which they wish to arrange in syste- 

 matic order all minerals of a capillary, bacillary, dendritic, or spicular 

 form, or such as compose oviform, rcniform, or tubular stalactites, in 

 which the spherical shape would be ascribed to a kind of attraction, 

 while the stalactitic would be confounded with that of adhesion and crys- 

 tallization. Other savans, on the contrary, have carefully separated 

 crystals, and have regarded all the other forms as modifications of amor- 

 phous structure. A few months ago, the Academy of St Petersburg heard 

 a remarkable note read to them from a distinguished observer (M. Par- 

 rot) who after having examined a rich collection of Imatra stones, con- 

 duct* d that they must be regarded as an extinct family of molluscs de- 

 void of shells, and of the most simple organization, to which he desired 

 to a m#ii the name Imutru. 



