PERKNITE {LIME-MAGNESIA ROCKS) 51 1 



may be very little lime present and yet they would not be peri- 

 dotite. This brings us to the re-definition of peridotite, and I 

 should define a peridotite chemically as a magnesia rock with 

 usually less than 6 per cent, of lime. This would put a rock 

 composed entirely of hypersthene or enstatite with the peri- 

 dotites, where they certainly belong chemically. 



H. W, Turner. 



San Francisco, Cal., 

 June 20, 1901. 



