EHRENBERG ON METEORIC AND VOLCANIC DUST. 13 



not resemble the pumice or slag, but is singularly like, both in colour 

 and material, the ashes that formed the first product of eruption at 

 Hecla on that day. The dust derived from scraping the ashes also 

 resembles in form the minute particles of the dust in question. 



2. Numerous other ashes examined by the author, and amongst 

 the rest that obtained from the new and afterwards sunk island of 

 Ferdinand, exhibit a different appearance. 



3. Amongst the particles of dust fallen occur siliceous organic 

 bodies of freshwater origin, and precisely in the same way we find 

 within the cells of ashes from Iceland, earthy matter filled with 

 recognizable forms of freshwater siliceous infusoria. i 



4. In the recently erupted products examined there are on the 

 whole twelve species determined, three of them doubtful, but nine 

 identical with known organic bodies. 



5. It is hardly probable that a sailing ship coming from Iceland 

 should bring with it on its deck as far as the Orkney Islands dust 

 or bog earth from the land in such a manner, that in sweeping up 

 the meteoric dust a mixture with this earth should have taken 

 place, and it is equally unlikely that the specimens of ashes should 

 have been collected from a morass. The specimens also themselves 

 were not at all dirty. A mere accidental resemblance between the 

 ashes and the dust is a third improbability not more to be admitted 

 than the others. 



6- At the same time it is not to be denied, that the material for 

 these investigations fails somewhat in absolutely authentic evidence 

 with regard to the source whence it was obtained. Since similar 

 investigations have not always conducted to the same result, the 

 necessity of obtaining greater certainty with regard to this point, 

 will be manifest. 



7. There is every reason to suppose, both from external and in- 

 ternal evidence, and also from the condition, altered by heat, of 

 many forms, that the mixture of organic bodies takes place imme- 

 diately in the volcano, and is not an accidental and subsequent 

 intrusion of foreign particles. 



8. If it is the case that organic bodies are certainly present in 

 the substances thrown out by volcanoes in recent eruptions, all those 

 objections must fall to the ground which assume a long period 

 during which infiltration went on into old deposits, as necessary to 

 account for the presence of minute foreign organic bodies in them. 

 As, however, the skilful mineralogist does not allow himself to be 

 deceived by the infiltration of particles, and distinguishes an incrus- 

 tation from a nucleus, so the microscopic observer is able to separate 

 the accidental from that which is original and real, and can distin- 

 guish the essential from the non-essential. 



9. Although the well-known and loosely compacted chalk is com- 

 pletely penetrated by water, and has often been for ages exposed to 

 all kinds of aqueous action, the siliceous-shelled animalcules are 

 never found in it, while the infusorial cases in the chalk marl, al- 

 though so long exposed, are often smooth and fresh as if they had 

 just been left by the animal. 



