370 Profs. King and Kowney on 



rods though their substance is changed, and hence are true 

 pseudomorphs, the former not improbably belong to the same 

 category — that is, of chemical changes without alteration of 

 original shape. Again, the statement that " the structure of 

 the dolomite in this specimen," presumably either figure 4 or 

 5 in plate viii., " indicates that it first lined the canals, and 

 afterwards filled them," is strongly in favour of our suggestion. 

 Dr. Dawson has added to his notice of the structure of the 

 dolomite that he has observed the same " appearance in larger 

 canals filled with serpentine." Ought not this fact to have 

 suggested the pseudomorphic or methylotic origin of the sub- 

 stance composing the "canals in dolomite"? 



In addition to the evidences above adduced, we may refer 

 to some others occurring in a specimen of ophite, collected by 

 Mr. W. King, jun,, in the Madras Presidency, in which the 

 serpentine (green, amoi-phous, and translucent) is broken up, 

 through disintegrating or chemical action, into a variety of 

 fonns — lamellar, lenticular, spheroidal, and cylinda-ical, all more 

 or less lobulated. Confining ourselves to the cylindrical forms 

 (some of which are long, while most of them are short), they are 

 surrounded either with calcite, or white flocculent serpentine — 

 that is, in the disintegrated condition. A transverse section 

 shows some to be composed of ordinary serpentine ; most of 

 them, however, are more or less changed, the change (manifested 

 by disintegration) commencing in their axis or at a point in 

 their centre. This point, which is white and flocculent, gene- 

 rally goes on enlarging until there is a large core enclosed 

 within a thin sheet of green serpentine ; and the sheath in 

 many instances gradually decreases until it disappears alto- 

 gether. The core also undergoes a change, calcite taking the 

 place of the flocculent serpentine ; and the change goes on, as 

 exemplified in a number of instances, until the entire cylinder 

 is converted into calcite. This is demonstrated by decalcifying 

 the specimens, in which case such cylinders, when surrounded 

 by serpentine, whether compact or flocculent, are represented 

 by cylindrical cavities ! 



We have in these examples a repetition of the process which 

 developed the rods in the Lizard serpentine, with this diflfer- 

 ence — that in the latter saponite is one of the products of the 

 process, while in the former we have clear, and it may be 

 positively asserted the clearest, evidence of a process which 

 we fully believe will thoroughly explain the origin of the so- 

 called " canals filled Avith dolomite," whenever the existence 

 of any thing of the kind can be demonstrated. 



