102 On the Composition, Structure, and Formation ofBcekite. ' 



These lines arc referable rather to the effects of pressure than to 

 an organic origin, — the frequent angularity of the specimens 

 pointing in the same direction. 



In a fragment of a silicified Pecten from the Greensand of 

 Haldon, Devon, the elevated ridges, characteristic of the shell, 

 are preserved intact, notwithstanding the complete displacement 

 of the carbonate of lime by silica, and the assumption by the 

 silica of that arrangement in concentric rings characteristic of 

 most Beekites. In the present specimen of shell, some of the 

 systems of rings are partly situate in a furrow of the exterior 

 surface, bend upwards, and follow the curve of a ridge, and then 

 dip into another furrow : the inner aspect of the shell being 

 level, shows no corresponding contortions of the systems of con- 

 centric ridges. In like manner, in the Beekite proper, silica 

 displaces rather than increases the original substance, — for the 

 organic structure is generally traceable in every part of the 

 tubercles and ridges, even to their summits, — being in fact more 

 conspicuous on the exterior surface of most of the hollow speci- 

 mens than on their interior. 



The tendency to deposition in a circular form, though not 

 peculiar to this substance, is seen in many other varieties of 

 silica — stalagmitic quartz or quartz-sinter, for instance, such as 

 that from the Geysers of Iceland, and the hot springs of Luzon 

 in the Philippine Isles. A specimen from the latter place is 

 represented in figs. 5 & 6. Eyed agate (fig. 7) shows the same 

 arrangement. Ploat-stone from Menil Montant, near Paris, 

 when examined with a lens, often displays minute beads and 

 concentric ridges ; while menilite, or liver-opal from the same 

 locality, presents an appearance very closely resembling that of 

 the Beekite No. 9. 



The annexed letter from Dr. Gladstone, commenting as it does 

 on both the physical and chemical questions under discussion, 

 may not inappropriately conclude the present paper : — 



" My dear Mr. Church, — Your Beekites seem to me very 

 interesting, not only in a chemical and geological, but also in a 

 physical point of view, as affording a remarkable illustration of 

 the tendency of certain bodies to assume a globular form during 

 deposition. I say c deposition/ because it is evident that the 

 Beekites are not fossils owing their mammillated appearance to 

 the organic form which has been silicified, but are rather deposits 

 on some substratum, which may be a coralline, a sponge, a shell, 

 or even a piece of stone. Yet this deposition seems always 

 accompanied by the replacement of part, or the whole, of the 

 carbonate of lime by silica. 



" Many of the concentric globular deposits in your specimens 

 bear a striking resemblance to the globular deposits of carbonate 



