lOO 



HARDWICKE'S SCIENCE-GOSSIP. 



are about half an inch apart, and are in the midst 

 of a very recent incrustation. The edges of the fossils 

 are rough and angular (fig. 6S), proving that they 

 have been knocked about somewhat before finally 

 resting in peace in this vein. Minute fissures are 

 often seen crossing these fossils without throwing 

 them (fig. 69). In some parts of the rock so many 

 minute veins cross each other as to form a regular 

 network. Let us note an interesting instance in 

 which a vein of brown-spar has thrown two others 

 of white-spar (fig. 71), telling us, in clear characters 

 inscribed on stone, that the former was propagated 

 after the latter. 



AB (fig. 65) is probably the origin of these pink layers.. 

 They are noticeable even in the vein on the side of the- 

 large fissure. Whence came this colouring matter? 

 It was probably washed down from the old red sand- 

 stone, for, although the latter is really the older forma- 

 tion, at its junction with the mountain limestone at 

 Skrinkle Bay— a mile or so from here— it actually 

 overlaps the limestone, having been upheaved, to- 

 gether with the beds above it, fully 1 5° beyond the 

 vertical. Hence the newer beds actually lie below th« 

 older ones. 



A few yards inland from the fissure we have de- 

 scribed, and parallel with the stratification, there is- 



NE&E 



Fig. 66.— Plan. 





Fig. 65. — Cross-section of Fissure. 



Fig. 67. 



Fig. 68. 



The fissures and cavities in the limestone are filled 

 up chiefly with pure white calcite, crystallised in 

 rhombohedra, or crystalline and indistinct. The sides 

 of the open cavities are often lined with scalene 

 dodecahedra, known familiarly as " dog-tooth spar" 

 (fig. 70), which are transparent, pink, or brown- 

 coloured. Just outside the hanging-wall of the large 

 fissure a number of pink veins occur. .Some of these 

 are composed of rhombohedric crystals of calcite made 

 up of alternate white and pink layers. These agate- 

 like crystals are very beautiful, and arc worthy of a 

 place in any mineralogical cabinet. In the crystalline 

 veins this pink matter appears to form layers parallel 

 to the sides of the vein. The red earthy matter in 



a hollow in the limestone, a part of one side of whiclr 

 shows differently coloured layers of calcite arranged 

 concentrically, and yet the whole is crystalline. This 

 agate-like structure is from 2-3 feet long, and about 

 one foot wide. The opposite side of the hollow is 

 formed of stalactitic and mammillated masses of 

 calcite, all of which show a concentric structure. 

 Below this cavity, and parallel with it, can be seers- 

 transparent and almost perfect crystals of dog-tooth 

 spar, lining a stratum of the limestone. Both are 

 the result of comparatively slow action. In the first 

 instance, a large cavity having been formed in the 

 limestone, layer upon layer of calcite has gradually 

 helped to fill it up ; and in the second, two strata,. 



