354 M. Ehrenberg on the Forms assumed by 



still occupy their natural situation in various degrees of development, 

 and where J. collected numerous examples now submitted to the in- 

 spection of the Academy. Ever since that time these bodies have afford- 

 ed me a subject of study, and I have endeavoured to ascertain the laws 

 of their structure in two different ways ; first, by an analytical method, 

 attempting to determine their mechanical structure by means of delicate 

 microscopic examinations; second, by a generical method, endeavouring 

 to produce similar forms artificially, a task which in neither of these cases 

 had been previously undertaken. These two methods, although the 

 trials I have made long continued fruitless, are still attended with great 

 difficulties, and are but in their infancy, have not failed to present results 

 which appear to me worthy of being submitted to the Academy, and, ob- 

 scure though they still are, to merit not the less on that account a fa- 

 vourable reception. 



Formerly, in 1836, when I communicated the results of my analytical 

 observations by the microscope on the regular fundamental forms con- 

 stituting earthy and friable (tendrcs) mineral substances, I spoke, although 

 with reserve, of a phenomenon presented by certain minerals, of a re- 

 gular disposition shewn in certain very minute fundamental corpuscles 

 to form themselves into articulated rods and rings, which sometimes re- 

 minded the observer of the serial linear disposition of the free molecules 

 of bodies under the influence of magnetism, as in kalkguhr and meer- 

 schaum ; and at other times indicating a force acting with more or less 

 energy in a circle or spirally, as in kaolin and chalk. Microscopical 

 researches prosecuted since on these singular relations, have afforded 

 more extensive results, and the regular corpuscles of chalk, which I 

 had at first named granulated folia (gckcernte blcettchen) will henceforth, 

 in accordance with my recent works on the formation of chalk by micro- 

 scopic organisms, assume the particular and characteristic name of crystal- 

 loids. 



New and successful microscopic observations on the figured stones of 

 Egypt, have enabled me to ascertain that these configurations, resem- 

 bling the corpuscles of kaolin and chalk, but in gigantic proportions, 

 have in all probability been produced by the same agents as the cor- 

 puscles of the latter, only with 'grosser materials. In fact, we immedi- 

 ately recognise in these Egyptian formations, whether they be in rings, 

 discs, or spheres, and varying in size from an inch to a foot, the animals 

 of the chalk (for example, Textillaria globulosa) whose undissolved calca- 

 reous coverings have been subjected, in the progress of their formation, 

 to a. force which has disposed them in annular series. These are appear- 

 ances altogether different from those presented by the flints and jaspers 

 of Egypt, in which we meet with imbedded polythalames only here and 

 there. The latter are not the corpuscles themselves, but only their 

 form silicified by a chemical operation, the nature of which is un- 

 known to us. The small visible calcareous coverings obtained by acids 

 in the soluble layers of the figured Egyptian stones, shew distinctly that 



