58 PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 
The members of first are not decomposed by chlorhydric acid, and there is 
no peculiarity in the manner in which their constituent water functions. 
The members of second are (with one exception) readily decomposed by 
chlorhydric acid, and the mode in which a portion of their constituent water is 
held in combination is anomalous. | 
The first are to be regarded as constituents of the rock mass which 
contains them,—paragenetic in time with the minerals associated with them. 
The second are products of the degradation of the primal constituents of the 
rock, and are compounds of a more stable nature than the originals which yielded 
them through a destructive change. 
It has to be admitted that the minute granular or crypto-crystalline nature 
of certain of these minerals renders them extremely difficult of discrimination, 
but the above may safely be used as leading-lines for the separation of the two 
classes, and the distinctions which will enable us in future to identify the 
individual members will be noticed after the consideration of the whole. 
So far as I have yet ascertained, the following members of each of these groups 
occur in this country :— 
Chlorites. 
Glauconite. 
Talc-chlorite. 
Penninite. 
Ripidolite. 
Chlorite. 
Chloritoid. 
Saponites. 
Delessite. 
Chloropheeite. 
Hullite. 
Saponite. 
Celadonite. 
THE CHLORITES. 
Many of the denser “ chloritic minerals” are so crypto-crystalline in their 
structure that we can call in the aid of neither the goniometer nor the polari- 
scope in their determination ; we are thus confined for the most part to physical 
