PLATE X. 



Fig. a. 



(Sp. No. 32273. Natural size.) 



Photographic reproduction of the weathered surface of avariolite. This hrings out very clearly 

 the inainmillated surface of the rock, which is due to the dififereutial weathering of the varioles and 

 of the groundmass lietween them. The rounded character of the varioles, and their gradation irom 

 those of very small to those of much larger size can readily be seen. (Desc, p. 108.) 



Fig. B. 



(Sp. No. 32273. Natural size.) 



Reproduction of the polished surface of a yariolite. This is designed to show the circular 

 character of the varioles, and the fact that each is separate and distinct from the one adjoining it. 

 It can be seeu that some of the varioles have very dark and others much lighter centers. (Desc, 

 p. 108.) 



110 



