Rocks of Noyang. 65 



brightly polarising scales. Besides this there were also well- 

 marked flakes of muscovite. Throughout this rock there are 

 numbers of the minute oval or rounded brown and colourless 

 microliths, which I have found very frequently in the most 

 altered of the quartzose hornfels rocks. I treated a slice of 

 this rock with hydrochloric acid, with occasional boiling, for 

 a month. I found the ores of iron removed, the scaly 

 micaceous aggregates dull and evidently much acted on, but 

 the muscovite and the minute microliths were quite un- 

 affected. The scaly aggregates are probably of some chlorite 

 mineral. 



Another sample I found to be a foliated rock, the mass of 

 which was composed of a micro-crystalline-granular aggre- 

 gate, having the appearance of a, mixture of quartz and 

 felspar, associated with a colourless or pale green micaceous 

 mineral. In this mass I observed angular quartz grains, 

 some of which were fractured, so that the parts were no 

 longer optically in accord with each other. Surrounding all 

 the larger quartz grains, I observed a margin of secondary 

 quartz, which was not always in accord with the nucleus. 

 In examining these quartz grains, it seemed singular that the 

 oval or rounded microliths, which are probably mica, are 

 often within the quartz substance. Their formation thus in 

 the substance of a quartz grain seems at first sight incon- 

 ceivable. The observation that these quartz grains consist of 

 an original centre, and a subsequently deposited exterior, 

 removes the difficulty, and shows that these mica-microliths 

 could have been formed during the metamorphism of the 

 rock, and then sealed up by the secondary quartz. With 

 these quartz fragments were also pieces of felspar — angular 

 fragments lying with their longer diameters according to 

 the foliations. I am unable to decide whether or not to 

 consider these as examples of the regeneration of felspars 

 from sedimentary material. Their peculiar appearance, and 

 their manner of arrangement favours this, and indeed there 

 is no a priori reason that I know of against such a regener- 

 ation in contact schists ; but the fact remains that such 

 instances are of extreme rarity. 



In following down the Tambo River from the Noyang 

 ford, the contact between the igneous rocks and the sediments 

 is found where Rainy Flat Creek joins the river. The sedi- 

 ments at that place are converted into well-marked varieties- 

 of quartzose and micaceous hornfels, such as those which I 

 have already described. The hornfels has a clip to S 10° E at 



