J. ParJdnson — The Making of Quartz Schist. 263 



not easy to identify, including, however, calcite, zircon, specular 

 iron, and pyrites. Between crossed nicols we realize the shape- 

 lessness of the quartz grains, which interlock the one with the other 

 as irregular polygons without auy trace of an orientation. They 

 average -019 inch across. A slice taken from the very similar quartzite 

 of the Kutub, 11 miles south of Delhi, possesses less white mica and 

 associated minerals, and the quartzes are dustier and exhibit outlines 

 still more fantastically irregular. 



As in the preceding slide, although we find indications of undulose 

 extinction, this is the only sign of pressure, so that any crushing of 

 the grains which may have occurred has been almost entirely 

 obliterated. Now and then, indeed, we seem able to recognize that 

 the longer axes of the grains have a common direction ; but the 

 haphazard cross-sections show outlines sometimes almost of a horse- 

 shoe shape with waved edges, at others elongated with many 

 irregular projections. The quartzes contain many rounded spots 

 of felspar; these are unstriped, rather opaque, and often roughly 

 rectangular in section, exhibiting then an obscure orientation. So 

 far as it goes this last-named feature indicates rearrangement in situ. 

 An average size is -008 X "003 inch. A few brown zircon prisms and 

 some crystals of magnetite are found. A specimen from the top of 

 the ascent to Amber from Jaipur also contains felspar fragments, 

 in many of which polysynthetic twinning (extinction 15°) is still 

 discernible, but which also occur as rounded grains included in 

 a quartz crystal, and often are better defined than happens in the 

 preceding slide. 



The quartz contains rows of inclusions and gas cavities which 

 have a common direction and occasionally extend without interruption 

 from one grain to another. Strain shadows are inconspicuous, but 

 the parallel lines of inclusions indicate that the rock has been 

 subjected to a certain degree of pressure. The felspars, however, 

 appear not to have suffered in the least, and we find no attempt to 

 break up into mica and quartz. The slide contains also grains of 

 bluish-green tourmaline up to -016 inch in length, magnetite, zircon, 

 and a few elongated flakes of a green mica. 



These rocks form a group usually possessing a saccharoidal lustre 

 and close-grained texture, and are distinguished microscopically by 

 the absence of evidence of pressure and by the irregular outline of 

 the quartz grains. These outlines must naturally have been acquired. 

 in sit'u, the structure of the whole proving great alteration. 



Conclusions. 



The recent researches of Messrs. Adams and Nicolson on the 

 'Flow of Marble'^ are of considerable interest in the present 

 enquiry. 



In these experiments stumpy columns - of Carrara marble were 

 enclosed in tightly encasing jackets made of a material possessing 



1 "An Experimental Investigation into the Flow of Marble ' ' : Phil. Trans., 190 1 , 

 vol. 195 a, p. 363. 



2 An inch or rather less in diameter and about 1-5 inches in length. 



