574 MacKenzie — Analcite of the Crowsnest Volcanics. 



postulated conditions of partial pressure of the water vapor 

 might conceivably be realized under surface conditions, so that 

 even there analcite could form. 



Some of the Sardinian basalts recently described by Wash- 

 ington* are examples of rocks consolidating at the surface and 

 containing analcite, though it is possible that here, too, the 

 mineral is intratelluric in origin. The shackanite of Dalyf 

 may be also mentioned in this connection. 



With the facts of the original paper in mind, and their fur- 

 ther explanation here given, the primary nature of the analcite 

 of the Crowsnest volcanics can not be open to any reasonable 

 doubt. 



Massachusetts Institute of Technology, Boston, Mass. 

 Maroh 15, 1915. 



* Jour. Geology, vol. iv, pp. 742-753, 1914. 

 f Geol. Surv. Canada, Mem. 38, p. 411, 1912. 



