356 M. Ebrenberg on the Forms assumed by 



I shall now proceed, continues M. Ehrenberg, to the description of the 

 objects which have formed the basis of my observations. 



The first or principal basis of these observations was the stony Egyp- 

 tian formation mentioned above, belonging to the calcareous deposits of 

 Upper Egypt, which presents itself in abundance in the form of spheres 

 with a single ej*e, or a pair, connected as in spectacles ; this formation 

 occurs in a small horizontal deposit of marl in the midst of the calcareous 

 rocks of Dendera. These formations arc sometimes regular spheres 

 about a foot in diameter, but the greater part do not exceed three or 

 four inches, collected in considerable numbers, and resembling piles of 

 common balls, sometimes with the discs more or less flattened and regu- 

 lar, and the nucleus globular like an eyeball, surrounded with bourrelets 

 or concentric rings ; sometimes also the discs are double, and united 

 like the eyes of a pair of spectacles. The intermediate forms and transi- 

 tions from one to another are innumerable, but we find no other kind of 

 them. 



I have noticed a similar structure on many occasions ; among others, 

 in the silex of the chalk of Rugen ; in a stone greatly resembling that of 

 Imatra, coming from a sandstone-formation, like the figure eight lying 

 on its side eo , which has been deposited in the Royal Cabinet of Miner- 

 alogy, and was obtained from the Muschelkalk of Oberstrehlitz ; as well 

 as in a black sphere, seven inches in diameter, procured from the coal 

 formation of Ruhrthal, and which may be seen in the cabinet of the 

 Royal Administration of Mines. 



The recent and detailed description of the Finland stones of Imatra, 

 at the waterfall of the same name, has afforded, in connection with the 

 previous observations of Hoffmann, a pretty accurate idea of their forms, 

 which I have had no opportunity of studying personally. I examined 

 last year a very interesting and instructive collection of these regular 

 forms, belonging to Dr Willander of Tunaberg in Sweden, who, when 

 coming to Berlin, brought his collection with him, when he became aware 

 that I was occupied with the subject, and with much liberality placed it 

 at my disposal. The marl of Tunaberg is certainly a stony formation 

 completely free from crystallization, but at the same time the most regu- 

 lar that has hitherto been met with. According to Wallerius and Linnaeus, 

 such formations are named in Sweden malrekor or nakhrad. They are 

 distinguished, as all other similar objects were by Linuaeus, by the name of 

 tophus ludus and marga porosa. Finally, the editor of the works of this na- 

 turalist, in 1779 and 1783, Gmelin, has classed them systematically among 

 the most heterogeneous kinds of bodies. The forms of Tunaberg do not 

 appear to have been known above two years. They are met with near 

 Fada-Muhle in a deposit of fine blue clay, and they always present, in a 

 very accurate and striking manner, the character of animal structure, sug- 

 gesting the idea of petrified molluscs. 



Dr Willander presented me with 47 specimens chosen probably from 

 many thousands; M. Thamnau of Berlin also, who brought upwards of 



