682 On the Local and Relative Geology of Singapore, [July, 



its numcralogical characters, for I have not time nor means at present 

 to ascertain them carefully. It is soft and glistering like silk, and 

 leaves a powder on the fingers which exactly resemhles in appearance 

 the fine glistering powdery down from a butterfly's wing. In some 

 cases it is less dry and more argillaceous. With the exception of Cape 

 Rachado* it has almost everywhere been more or less penetrated in 

 bands (and broad spaces occasionally) by ferruginous gas which has 

 transformed it into one or other of the forms before described or some 

 intermediate forms. Dykes and veins of pure quartz and of quartz 

 with numerous fissures filled with an iron crust are frequent in some 

 localities, while in others they are wanting. Wherever these dykes 

 and veins occur the foliation of the schist is much contorted. In some 

 localities the surface is covered with black shining mamillated scoreous 

 blocks passing down into a lateritic mass, in which the schist is often 

 not greatly altered but is penetrated by ramifying dykes and veins of 

 a ferruginous, quartzose, or quartzo-ferruginous character. Isolated 

 pseudo-crystals and isolated plates of quartz occur in the schist in 

 some places, and, on the other hand, patches of the schist are found 

 in the hearts of large pieces of quartz. But it would require other 

 20 pages to give even an outline of the varied and irregular manner 

 in which the rock has been altered. If we did not every where come 

 upon portions of the original rock unaltered, or find traces of it in 

 the altered tracts, it would be almost impossible to believe that all the 

 varieties of the latter have had a common origin. I must briefly allude 

 to Cape Rachado. This is a bolder and. higher range than any found 

 elsewhere along the coast and projects far into the Straits. It is the only 

 locality which I have yet seen where the quartzose has predominated over 

 the ferruginous action of the plutonic gases. The rock every where ex- 

 hibits unequivocal evidence of its having been originally the same argillo- 

 micaceous schist which prevails over the rest of the region. In some 

 places the cliffs are almost wholly quartzose, — in others the rock is a con- 

 geries of quartz veins and foliae, — in others the seams between the 

 quartz folise have a coating of the original mica, — in others the original 

 mica predominates and the quartz is more sparingly scattered through it. 

 Broad dykes of compact quartz, of quartz mixed with a ferruginous 

 crust, of numerous parallel veins with quartz crystals springing from 

 * Where the plutonic action has been of a silicifying more than a fen-u^inating" nature. 



