MINRRALQGV; WITH A CLASSIFICATION OF SILICATES. 



SI 



Heuce, while for viuivaleut elements or monads like sodium, chlorine and fluorine, the 

 symbols represent the received equivalent weights, these weights for dyads like glucinum, 

 calcium, ferrosum. oxygen and sulphur, are divided by two ; for triads like boron, 



aluminium and ferricum by three, for the tetrads silicon, titanium, tin, zirconium and 

 thorium by four, and for a pentad like niobium by five.' Thus the numerical values of 

 the svmbols here used are as given above. 



III. 



Tribe 2. Protospathoid. 



§ 63. In the second tribe, which we have called Protospathoids, shown in table No. Ill, 

 are the sparry silicates of zinc and manganese, willemite and tephroite, and the ferro- 

 mangauesian species, knebelite, — all having the ratio of unisilicates. To these are joined 

 the double silicate of lime and magnesia, batrachite, with gadolinite, a silicate chiefly of 

 yttria, giving apparently the same atomic ratios, and helvite, a silicate of glucina and 

 manganese, remarkable for containing a large amount of sulphur ; in which respect it 



The formulas employed in calculating the values of P and V for the following species are as follows : — 



n. Danalite— (gl3.ofe2.omno.-zni.58io.o)Oi;.oS,.o c- Leucophanite— (cai-oglj.oHaj.oSiic-olOjs-o 



h. Gadolinite— (cae./e,..,ytc.j8is.„)o,(;.o d. TscbefiT<inite— [Pamonr] {cOu.c/e„.,„ca(,.,r,si,.3„ti„.;„)o3.oo 



