104 MICROSCOPICAL OBJECTS FOUND 



changes may be effected in the atomic structure 

 of calcareous rocks, and, consequently, in all the 

 microscopicorganisms not materially larger than the 

 amorphous atoms of the rocks, without involving 

 the destruction of their fossils. He has given an 

 interesting example of this in the little oasis of 

 fossiliferous Carboniferous limestone at Cos- 

 satchi Datchi in the neighbourhood of the Ural, 

 where a patch of limestone surrounded by erup- 

 tive rocks has been thrown up into calcareous 

 hummocks, an appearance compared by the author 

 to the hornitos of the Mexican Jorullo. This 

 effect Sir R. I. Murchison ascribes to heat and 

 gaseous vapours which formerly struggled for 

 expansion, and which have obliterated all lines of 

 stratification, and rendered the limestone as pul- 

 verulent as sugar ; yet it abounded in interesting 

 fossils.* In the valley of the Miass also he found 

 Encrinites in a pure saccharoid limestone, which 

 had also been highly altered by neighbouring, 

 eruptive works.f These instances prove how 

 large an amount of change may be wrought in 

 the atoms of a rock by gases, under the influence 

 of volcanic heat, without obliterating its larger 



* Geol. of Russia in Europe. Vol. i. p. 439. 

 t Idem, p. 42G. 



