494 



GEOLOGY. 



Fig. 375. — Section of a concretion (septarium) the cracks of which have been filled 

 by matter deposited from solution. About half natural size. (Photo, by Church.) 



Fig. 376. — Section of a concretion, the cracks in which have been filled by deposition 

 from solution. The filling appears to have wedged the parts of the original concre- 

 tion apart. The fillings are veins. Some of them show that the vein-material 

 was deposited on both walls. About half natural size. (Photo, by Church.) 



