Dr. J. E. Reynolds on certain Mineral Silicates. 275 



generally employed in expressing chemical changes. Bat little 

 attention has hitherto been given to these attempts to bring 

 mineral chemistry into accordance with other branches of the 

 science. This indifference may have resulted, on the one 

 hand, from a dislike to alter conventional modes of expression, 

 and on the other from the consciousness that the new formulae 

 were less simple, though perhaps more accurate, than those written 

 according to the old plan. Whatever the causes may have been, 

 the fact is that- few use the " new system " in writing the formulas 

 of minerals. That a change is most desirable I think few will 

 deny; the question really is how such can be advantageously 

 effected. The adaptation of the old formulas of the mineral 

 oxides, hydrates, sulphates, carbonates, phosphates, sulphides, 

 arsenides, &c. to those of the new system is a very easy matter. 

 But the alteration in the case of the silicates is very considerable ; 

 and since these bodies constitute nearly two-thirds of the solid 

 crust of the globe, it is of great importance that any formulas by 

 which their composition may be represented should be capable 

 of exhibiting the natural relations of individuals. 



We have already had the advantage of ascertaining the views 

 of Dr. Odling* on this subject, of Dr. Franklandf, Mr. Watts J, 

 M. Adolphe Wurtz §, M. Naquet||, and others; but it must be 

 confessed that we have not yet arrived at a satisfactory mode of 

 expressing the constitution of the silicates, notwithstanding the 

 amount of ingenuity and chemical ability which has been brought 

 to bear upon the question. 



Professor Dana, with his usual care and the clear appreciation 

 of scientific truth which marks his works, has entered largely 

 into the subject of the unitary formulas of minerals in the new 

 edition of his i Descriptive Mineralogy/ just issued from the 

 press. In most cases he gives the formulas of minerals on both 

 systems ; but in writing those of the silicates he departs to some 

 extent from the ordinary rules even of the new system, and adopts 

 the notation proposed by him in his recent papers on the sub- 

 ject^! . Whether the change is an advantageous one or the reverse 

 remains to be decided ; but since the new formulas, as given by 



* Philosophical Magazine, 1857. 



t Lecture Notes, 1.866, pp. 97 & 175. 



X Watts's 'Dictionary of Chemistry/ 1863, especially vol. v. pp. 240-263. 



§ Modern Chemical Philosophy. The valuable translation of this work 

 by Mr. William Crookes, F.ll.S. 1867, p. 157- 



|| Principles of Chemistry : founded on modern theories, translated by 

 W. Cortis : 1868, p. 135. In Naquet's work, only the hydric silicates are 

 treated of ; but these are regarded as types of the native metallic silicates; 

 hence the views of this chemist on the constitution of most of the latter 

 salts can be inferred from his statements in reference to the former bodies. 



H American Journal of Science, vol. xliv. pp. 145, 252, 398. 



T 2 



