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Located in a mountainous area of Guizhou province in southwestern China, Qiannan is known for phosphorite, black sticky rice and delicious quail.

He was desirous of observing the effects of the numerous changes that have taken place in that country since the death of Ferdinand; and he, at the same time, thought that his assistance and previous knowledge of the country and people, would be useful to a scientific friend, Dr Daubeny, who had been commissioned by the Agricultural Society to examine the formation of phosphorite in Estremadura.

On these the travellers reach Logrosan, where is situate the vein of phosphorite that it was one of the objects of their journey to visit.

This apatite, or phosphorite, is found in certain parts of the world in large masses; but as a rule, it only occurs in small quantities in most rocks.

Now, the solubility of Thomas-slag in citrate of ammonia was found by Professor Wagner to be no less than 74 per cent, while that of phosphorite only amounted to 4 per cent.