MacKenzie — Analcite of the Crowsnest Volcanics. 571 



Art. XXXIX. — The Primary Analcite of the Crowsnest 

 Volcanics ; by J. D. MacKenzie. 



The writer recently published a description of some analcite- 

 bearing pyroclastics which occur in southwestern Alberta,* 

 and interpreted the nature of the analcite as primary. In the 

 light of the facts of the occurrence as fully described in the 

 publication referred to, it was not thought necessary to con- 

 sider the hypothesis that the analcite might be secondary. 



However, in a recent number of this Journalf a review 

 questions the writer's conclusions and suggests that what is 

 now analcite may have been originally leucite, and that it has 

 become converted to analcite by sodium solutions, through a 

 process the possibility of which is suggested by Lemberg's 

 experiments. The reviewer's questions are principally based 

 on a misinterpretation of the conditions of deposition of the 

 pyroclastics as described, and also to an inferred doubt that pri- 

 mary analcite could form under the conditions of eruption. 



It is the intention of the present note to show : (1) that 

 under the conditions described there is no reason to suppose 

 the conversion of the analcite to be probable ; (2) that the 

 possibility of conversion is doubtful, even with conditions such 

 as the reviewer imagined ; and (3) that it is quite possible for 

 analcite to form under the conditions described. 



(1) In the article under consideration \ the writer, when sum- 

 marizing the conditions of deposition of the Crowsnest volcan- 

 ics, stated that : 



"... the area they now cover was occupied by a 

 shallow sea probably of fresh water ....," 



the evidence for this conclusion being given elsewhere in the 

 article. It might have been better to have used the term 

 " lake " instead of " sea," and a further ambiguity is introduced 

 two lines below by the word "submarine"; this should be 

 " subaqueous." Despite these inaccuracies of statement, it 

 seems clear from the context that the volcanics were described 

 as having been deposited in fresh water. However, the evi- 

 dence for the character of the water is not conclusive, and it 

 may have been brackish, or salt ; nevertheless it was more 

 probably fresh, and was so described. Thus, the assumption 

 by the reviewer of " solutions of sodium salts " is not justifi- 

 able from the writer's description, and the evidence in hand 



* Geol. Surv. Canada, Mus. Bull. No. 4, Geol. Series No. 20, Nov. 19, 1914. 

 + Vol. xxxix, p. 222, February, 1915. 

 % Op. cit., p. 13. 



