1919.] Wild and Speight.—Limestones of Canterbury. 189 
No. 1. Upper hard band of limestone in gully south of Waihao River, near 
Waihao Forks. 
No. 2. Lower band of limestone, same locality. 
No. 3. Composite sample, outcrop parallel to railway, Waihao Downs. 
No. 4. Calcareous greensand, along the railway between Waihao Forks and 
Waihao Downs ; sample 8-10 ft. above the greensand ; rock 
filled with casts. 
No 7. Weka Pass stone, 8 ft. above junction with Amuri limestone, at 
Weka Pass. 
No. 8. Weka Pass stone, 2 ft. above junction, near viaduct. 
No. 9. Amuri limestone, 4 ft. below junction, near viaduct. 
No. 24. Marly development of Amuri limestone at Weka Pass. 
No. 28. Amuri limestone, 2 ft. below junction with Weka Pass stone. 
No. 30. Lower 2 ft. of Weka Pass stone. 
No. 13. Amuri limestone, 2-4 ft. below contact with “ grey marl,” old wharf, 
Kaikoura. 
No. 14. Amuri limestone, at contact, old wharf, Kaikoura. 
No. 15. “ Grey marl,” 2-4 ft. above contact, old wharf, Kaikoura. 
No. 17. “ Grey marl,” at contact, old wharf, Kaikoura. 
No. 19. Upper layer of glauconitic limestone, Maori village, south side of 
Kaikoura Peninsula. 
No. 20. Layer of glauconitic limestone just above nodular layer, Maori 
village, Kaikoura. 
No. 10. Nodules at bottom of contact layer between Amuri limestone and 
Weka Pass stone, at Weka Pass. 
No. 11. Nodule at middle of contact layer. 
No. 12. Nodule near top of contact layer. 
No. 16. Nodules from Amuri Bluff. 
No. 18. Nodules from Amuri Bluff. 
No. 22. Nodules, east of Maori village, Kaikoura. 
No. 23. Nodules from Weka Pass. 
No. 32. Nodules from Boundary Creek and Motunau River. 
A number of other analyses are recorded in various Geological Survey 
and Dominion Laboratory reports, and in the New Zealand Journal of 
Agriculture (see in particular Journ. of Agr., vol. 11, p. 328). 
Reasons for the Low-grade Character of the Limestones. 
It will be readily seen from the results of the analyses that the amount 
of phosphate contained in the rocks is nowhere large enough to warrant 
them being called high-grade phosphates. This is a fact generally true 
for limestones in other parts of the world, but circumstances sometimes 
occur which favour a concentration of the phosphate till the deposit 
becomes commercially valuable. 
One of the most important of these circumstances may be referred to 
as differential solution. Calcium carbonate is more soluble in water con¬ 
taining carbonic acid than is calcium phosphate or any other combination 
in which phosphorus usually occurs in nature. Hence on a surface which 
is exposed to the solvent action of water there is likely to be a concentration 
of the phosphate if the shape of the upper surface is favourable for its 
