566 Notices of Memoirs — ' China Clay ' a Mineral. 



mechanical combination. I cannot myself see that it is any answer 

 to this contention to say that in the china clay of commerce there is 

 still to be found a proportion of the other materials with which the 

 clayey substance was originally completely combined. Take, for 

 example, the presence of mica ci-ystals in the commercial china clay. 

 It is admittedly one of the objects of the washing process to separate 

 the clayey substance from the mica, and this to a large extent is 

 achieved, but because it is not wholly effected, and because the china 

 clay is merchantable, notwithstanding the continued presence of some 

 mica crystals, can it logically be asserted that mica is an essential 

 constituent of china clay ? I cannot bring myself to adopt any such 

 view. In my opinion china clay or kaolin is the clayey substance in 

 the china clay rock representing the decomposed felspar, and the mere 

 fact that in the process of separating and extracting it from the rock 

 a condition of disengagement is reached which is sufficient for 

 practical commercial purposes, and beyond which it is therefore 

 unnecessary to prolong the process, cannot, in my opinion, alter the 

 real nature of the substance or convert the resultant product from 

 a natural substance into an artificial combination of diverse elements 

 originally combined in wholly different proportions. 



On the evidence, therefore, I come to the conclusion that china clay 

 is a natural product — that is, the substance representing felspar in 

 granite which has been converted into china clay rock by the complete 

 decomposition of one of its three essential constituents. The question 

 I have now to decide is whether such a clay as I have described is 

 a mineral. It is common ground that it has been so regarded by 

 geologists, mineralogists, and textbook writers for very many years 

 past, not only in this countiy, but in America, France, and Gennany. 

 Jameson as early as in 1820, Professor Lapworth himself as late as 

 in 1899, and Dr. Hatch and Professors Dana and Miers — the latter 

 the well-known Professor at Oxford — at intermediate dates are all 

 responsible for well-known and authoritative works, wherein it is 

 classed as a mineral. It is true that when the witnesses for the 

 railway company were confronted with these authorities they drew 

 a distinction between kaolin and the china clay of commerce, and 

 suggested that the former might possess attributes which would 

 qualify it as a mineral, but which were not to be found in the latter ; 

 but I attach no importance to this distinction, in that I regard kaolin 

 and china clay as convertible terms, and the mere fact that the clay 

 can be turned to commercial uses without being altogether dissociated 

 from foreign substances cannot, in my opinion, alter its real character. 

 But the question does not really rest on the printed authorities to 

 which I have just alluded. The scientific witnesses who were called 

 on behalf of the railway company frankly admitted that down to some 

 time in the latter part of last year they shared in the generally 

 accepted view that kaolin or china claj^ was a mineral. Indeed, in 

 a case tried in 1904 — North British Kailway Company v. Turners 

 (Limited) — Professors Boyd Dawkins and Lapworth, two of the 

 witnesses who in this case have been called to prove that it is not 

 a mineral, gave evidence that kaolin or china clay — treating the two 

 words as synonymous — is a mineral of a definite chemical composition, 



