126 



pressed my belief that many of these were formed prior to the 

 deposition of the rock in its present form ; as a microscopic 

 examination of thin slices of the rock shewed that crystals occur 

 with distinct traces of the kind of attrition that would be produced 

 by rolling, and with both the worn and the unworn portions of the 

 crystal alike coated with the film of Haematite that is generally 

 supposed to have been produced contemporaneously with the 

 deposition of the rock material itself. 



That other crystals occurring in the same rock have been 

 actually built up around grains of sand in situ, and subsequently to 

 the formation of the rock, I am now quite convinced from a 

 microscopic examination of other preparations of the rock shewn 

 me by my friend Mr. WilUam Atkinson of Penrith, and by Mr. 

 John Arthur PhilUps, F.R.S. 



^ To be continued. ) . 



