Andrew. — On the Clarendon Phosphate-deposits . 453 



the district they lie almost horizontal, though a slight inclination 

 towards the south is noticeable on comparing the altitudes of 

 the outcrops at different points. As the outcrop recedes from 

 the plains, however, it becomes more and more elevated : this is 

 best seen on the western outcrops, where the limestone rises 

 300 ft. in a horizontal distance of a mile ; at the highest outcrop 

 the dip is seen to be S. 42°, E. 8°. On the east side of the road 

 the calcareous strata dip steeply towards the schist, the dip 

 varying from 15° to 45° in an easterly direction (E. 10° S.). There 

 are three sets of well-developed joints, which aid the quarryman 

 greatly in his work. 



The top of the calcareous series has a very irregular surface 

 of projecting pinnacles and deep depressions, which have been 

 formed by the action of percolating waters containing carbonic- 

 acid gas (C0 2 ) ; these have carried away the calcium-carbonate 

 in solution, the greatest action having taken place along those 

 channels where the percolation was strongest. As the mode of 

 weathering throws considerable light on the question of the origin 

 of the rock-phosphate, I will not describe it fully until discussing 

 the origin. 



Millburn Quarry. — The calcareous rocks are well seen in the 

 Millburn .quarry. The sequence of the various bands here was 

 worked out in full, as I hoped to find a similar sequence in the 

 other limestone outcrops of the districts. A general but not an 

 exact resemblance was found ; and I publish here the result of 

 this work, in the hope that future workers may be aided by it 

 in attempting to trace the sequence of the various bands in this 

 district, and perhaps also in other districts. The typical sequence 

 consists of the following, starting from the top : — 



H (30 ft.). Siliceous limestone with glauconite-grains through- 

 out ; Brissus (Meoma) crawfordi the chief fossil. 



G (3 ft.). Hard limestone, less siliceous than H, with few 

 fossils and no glauconite-grains. 



F (2 ft.). Hard tough limestone, fairly siliceous : Ostrea 

 wvllerstorfii in abundance. 



E (6'5 ft.). Tough limestone with Magellania sinuata. 



D (3 ft.). Very pure knubbly limestone, with broken frag- 

 ments of shells of Brachiopoda. 



C (42 ft.). Pure white limestone, with Brissus {Meoma) craw- 

 fordi, Pecten hochstetteri, and remains of vertebrates. 



B (35 ft.). Limestone, pure at first, but becoming more and 

 more glauconitic towards the base, where it merges 

 into A. 



A. Unknown thickness of glauconite sands, with very few 

 well-preserved fossils. 



