200 W. A. Tarr — Cone-in-Cone. 



are due to gases rising through the muds. A view similar 

 to that of Young has been expressed by Lawson. This 

 view has been adequately disproved by Gresley and 

 Harker. 



After a careful review of the literature on cone-in-cone 

 the writer feels that there are still many points upon 

 which more data are desired. He has studied a suite of 

 specimens from many places, and it is the object of this 

 paper to give the results attained, in the hope that others 

 will give some attention to a very difficult, yet extremely 

 interesting problem. 



Description of Cone-in-Cone. 



The general features of cone-in-cone are essentially the 

 same for all occurrences. This similarity is true even of 

 the minor features of the structure. The structure con- 



Fig. 1. Fig. 2. 



Fig. 1. — Cone within cone. 

 Fig. 2. — Single cone. 



sists of a series of right circular cones, which may fit 

 one inside the other (fig. 1). This is the common mode 

 of occurrence, but cones may also occur singly (fig. 2). 

 They are usually grouped along a plane (fig. 3), which, 

 if it occurs on the surface of a concretion, may be curved 

 to fit the surface (fig. 4). Cone-in-cones are usually asso- 

 ciated with concretions and in areal extent are generally 

 co-extensive with them. The writer has observed this 

 structure in concretions five feet in diameter. The cones 

 are generally perpendicular in the central part of the 

 layer (at a in fig. 4), but near the edge they are inclined 

 (as at b, fi.g. 4). 



