the Process of Petrifaction. 81 



when calcined they yield more than trees. If we proceed in this 

 way we shall in future possess in chemistry an important and 

 serviceable assistance for the determination of fossil plants, as we 

 slwU be authorized, by the experiments detailed above, to de- 

 clare with certainty that plants rich in potash can never be 

 petrified ; an assumption we are so much the more entitled to 

 adopt, since the experiment with the fossil fern proves, how, in 

 this respect, the vegetation of the ancient world corresponds with 

 the vegetation in the present day. I intend to examine in this 

 manner the most important families of the vegetable kingdom, 

 and I hope, by means of this synthetical method, to attain many 

 desirable conclusions regarding the analogy of many yet doubt- 

 ful natives of the ancient world. 



Animal bodies, as dry fibrous muscles, can also be altered in 

 this manner, but whether they can be converted into another 

 substance I do not venture to assert ; but the experiment suc- 

 ceeds with insects, as with flies, gnats (whose more delicate 

 parts, the wings and feelers, are well preserved), the muscles 

 of crabs, and also with infusory animals. Thus I saw quite dis- 

 tinctly a species of Daphnia (from the half putrid water of a 

 water-barrel) which had been placed in a solution of iron, be- 

 come converted into iron after being exposed to a red heat for 

 half an hour, and even its feet were thus changed. If, then, we 

 were to place infusory animals, whose skeletons did not consist 

 of silica, in a siliceous solution, and then heat them to a red heat, 

 we might be able to form artificially Bergmehl, tripoli, and 

 polishing slate, whose composition has recently been unfolded by 

 the extremely important discovery of Ehrenberg. Evidently 

 here also the larger or smaller quantity contained by the animal 

 organs of solid materials insoluble in water (viz. phosphate of 

 lime) would exercise great influence on the success of the experi- 

 ment. In the parts richly provided with fat, that substance 

 would oppose insuperable obstacles to the preservation of the 

 form, for during the heating it would swell out and change the 

 whole into a formless mass. I intend to prosecute also these 

 experiments ; and, in the mean time, we may perhaps regard 

 tlie last mentioned circumstance as the reason that animals of a 

 higher class cannot be petrified. 



The experiments now communicated seem to me to throw an 



VOL. XXIII. NO. XLV. JULY 1837. F 



