220 ME. J. PAEKINSON ON THE HOLLOW SPHERrLITES [May I9OI, 



111 one or two instances a thin arc of quartz separates the inner 

 spherulitic zone from the mottled fibrous material surrounding it ; 

 in others, curved or branching lines traverse the latter, and define 

 a series of spaces, each possessing a distinct fibrous growth which 

 differs in direction from that of adjoining areas. Such quartz-filled 

 arcs and lines may be hest accounted for by the supposition of 

 contraction round a vesicle as described by Prof. Bonney.^ 



In another example the greenish material, but faintly mottled 

 and with practically no radial structure, appears to have resolved 

 itself into a number of globular forms roughly connected one with 



Fig. 3. — Parts .of two rings of a litliopliysa from the Wrockwardine 

 district^ showing the fibrous felspathic outgrowths. xSO. 



<«v> •♦ 





.4 i >0Mmm}^^p-' "'^m^s^^^^m^i^^^''--m 



f.''.^/-' 



'.iy:'-'f->!>}fi 



i-**';j.iJ:^';':ijf 





[Undotted spaces are filled with quartz.] 



the other. A very confused crystallization, resembling that seen 

 before, occupies the interspaces : these, for the most part, consist of 

 discoloured quartz, separated indistinctly from the greenish matrix, 

 Avhich often seems produced outward into them in a hazy 

 indefinite way. Embedded in the interspaces are the remnants of 

 lath-shaped crystals, now entirely replaced by secondary products, 

 and scarcely to be distinguished between crossed nicols from their 

 surroundings. These, I think, are felspars ; and I am led to this 

 identification by comparison with other slides where an indubitable 

 felspar has been altered in exactly this way.^ 



In other sections we find long lath-shaped crystals projecting 

 into, or apparently lying altogether in, a cavity. They consist of a 

 skeleton of iron-oxide, recalling the common alteration-product of 



^ Quart. Journ. Geol. Soc. vol. xxxviii (1882) p. 289. 



2 See 7th Ann. Eep. U.S. Geol. Siirv. (1885-86) p. 267, for the description 

 of felspars m the lithophjsa; and the cavities connected with them in the 

 Yellowstone region. 



