BY A. B. WALKOM. 



167 



Petrology. — Only one crystal was sectioned for the microscope. 

 It consisted almost completely of granular calcite. A small pro- 

 portion of the calcite-grains are clear and colourless, but most of 

 them are of a cloudy-brown colour. A few small fragments of 

 quartz were observed. 



Summary and Conclusions. — All the observations made on these 

 glendonites from the Lower Marine Series, confirm the conclusion 



Fig.5. — Freehand drawing Fig.6.— Same as Fig. 5 (side 



of glendonite crystal, view : about nat. size), 



showing direction of 

 striations (front view : 

 about nat. size). 



arrived at by Professor David, Dr. Woolnough, and Messrs. Taylor 

 and Foxall, that the original mineral, of which they are replace- 

 ments, was glauberite.* Nothing has been observed which conflicts 

 with their conclusions, excepting numbers (v.) and (vi.).f 



With regard to (v.), which is as follows, "The presence of 

 numerous erratics indicates that these waters were occasionally 

 chilled by floating ice," it may be stated, that three, of the four 

 newly-discovered occurrences of glendonite, are on horizons which 



*Op. cit., p. 179. 



fOp. cit., p. 178. 



