he, Ko Sr ee ee 
and the Products of its Transmutation. 141> 
The quantities of oxygen were— a nf 
Silica, ‘ — 20°06 3 
Alumina, . 8°98 | 
i voxide of 3 frome 4-86 { ae ? ue 
Lime, : : 6°45 
Magnesia, : 0-10 ; 
Potash, . |. 004 SP aR 
Soda, : ‘ 0-11 
- The composition of this mineral agrees with the general 
formula proposed by Rammelsberg for epidote more closely 
than any hitherto analysed. } 
Among the pseudomorphous substances produced by an 
interchange of constituents, the number of instances in 
which the product of alteration is a double silicate is very 
small. Apart from the remarkable pseudomorphous felspar 
recently discovered, and the pseudomorphous zeolites, the 
only double silicates which occur as pseudomorphous are 
mica, hornblende, chlorite, and epidote. The first two vary. 
so much in their composition that they can scarcely be re- 
garded as double silicates, of definite simple constitution, so 
that there remain only the pseudomorphous chlorite and 
pseudomorphous epidote, in the forms of garnet and Wer- 
nerite. The compositions of these latter minerals possess a 
certain similarity. Their formule are :— 
Meionite, RO SiO, + 2 R, 0, SiO, 
Garnet, ; RO SiO, + -R, 0, SiO, 
Pseudomorphous epidote occurs only in the forms of these 
two minerals, and it might be supposed that the similarity 
in their composition would furnish some clue to the mode of 
alteration. Thus meionite and zoisite being heteromorphie 
substances, it might be assumed that the conversion of the 
former into the latter consists in a physical re-arrangement 
of the molecules, attended with an increase of density. 
This cannot, however, be the case, and for the following 
reasons :— 
- 1, Although zoisite and meionite are identical in composi- 
tion, pistacite and meionite are not; meionite does not con- 
tain peroxide of iron, while in pistacite it seldom te to 
less than 10 per cent. 
2. There is nothing to justify the opinion, that the origi- 
