96 Rev. A. Sedgwick on the Geological Relations and 



each solid angle is the acumination of a distinct bundle of crystalline fibres diverging from a 

 centre. 



Some of these masses have been erroneously called stalactitic. They have not the structure of 

 stalactites ; for they are not made up of successive layers arranged about the axes of the elon- 

 gated pendent cones, but on the contrary (where the crystalline structure has not been carried 

 too far) we may find them made up of circular plates piled upon each other, with their planes at 

 right angles to the same imaginary axes ; and these plates seem to be the prolongations of the 

 laminae of the contiguous beds. 



The concretions on the sides of the cells are often extremely beautiful, and are generally com. 

 posed of imperfect spheres or clusters of spheres. They never stand out in elongated forms like 

 those last described, because the laminai here present their edges to that face of the rock on which 

 the concretions are aggregated. They are generally more crystalline than the preceding class, 

 and the crystalline parts are arranged nearly in the same manner. A fracture through the centre 

 of one of these clusters of spheres often exposes a structure of great beauty. The whole mass is 

 found to be made up internally of a congeries of spheres of various sizes, compressing, interrupt- 

 ing, or penetrating each other ; and each sphere is composed of separate bundles of diverging 

 crystals acuminated (wherever the process is complete) by the acute solid angle of the inverse 

 rhomb. Yet even through such masses as these, we may often trace the original lines of laminated 

 or slaty texture : and when they are struck off" from the wall to which they are attached, we may 

 see them passing into the rock, partaking of its inequalities, and penetrated by its cells. They 

 have then a singularly complex structure, being at one and the same time crystalline, earthy, 

 cellular, slaty, and globular. 



The last set of concretions to be noticed in this place, are found in association with the dolo- 

 mitic earth occupying the cells, are unattached to the surrounding beds, and are always of a more 

 or less perfectly spheroidal form. Sometimes they are single ; but more frequently several spheres 

 are in contact, w hich by mutually penetrating each other, produce a number of grotesque forms ; 

 and occasionally they are grouped in beautiful regular clusters. In general they are less crystal- 

 line than the globular masses before described, and they do not exhibit the same kind of laminated 

 structure; but in some instances they are studded with the projecting angles of the inverse rhomb, 

 and on fracture are found, as in the former instances, to be composed of diverging bundles of 

 crystals. The largest of these concretions (which at Fulwell Hill are sometimes more than a foot 

 in diameter) have commonly a smooth surface ; and when broken in two, expose a number of 

 thick ill-defined concentric layers, which are either aggregated about an earthy nucleus, or are 

 hollow in the centre*. These layers are of various colours; ash-grey, smoke. grey, yellow, or 

 dark-brown. Towards the centre, the fracture is usually dull and earthy ; but towards the cir- 

 cumference, the layers are made up of many curved crystalline plates, and the lustre is shining. 

 In other instances, balls of considerable size have the internal structure here described, while 

 their outer zone is made up of diverging crystalline fibres, with the usual acumination. The 

 transverse fracture in such cases is very beautiful. 



These spheroidal concretions are in some places subordinate to the pulverulent matter ; in 

 others, they abound so much that they nearly fill the irregular cells; and the ochreous powder 



* In such cases the original nucleus has probably been carried off ; like the shell which leaves 

 only its cast in the rock, or the crystal which leaves only its impress on a secondary investing 

 pseudomorphous substance. All these seem to be examples, on a small scale, of movements among 

 the particles of solid bodies which are in contact, and of new crystalline arrangements, without 

 the intervention of any previously chemical solution. 



