168 GLENDONITE FROM THE LOWER MARINE SERIES. 



are not considered to have been formed under glacial conditions. The 

 newly-discovered occurrences also do not agree with the statement 

 in conclusion No. (vi.) that "The horizons of the glendonites are 

 not far below, in some cases close to, the top of the highest beds of 

 a Marine Series, etc." 



Glendonite has now been recorded from seven horizons in New 

 South Wales, and one in Tasmania. These horizons are scattered 

 at intervals, through a thickness of strata amounting to about 7,000 

 feet. This shows that the conditions, which governed the crystal- 

 lisation of glauberite (for it is almost certain that this was the 

 original mineral), must have been of fairly frequent occurrence in 

 the Permo-Carboniferous seas; and it also shows that the occur- 

 rence of the pseudomorphs is of no value as an indicator of any 

 particular stratigraphical horizon. 



Glacial conditions were of frequent occurrence during Permo- 

 Carboniferous time, and Professor Woolnough has suggested, in 

 conversation about these pseudomorphs, that these conditions may 

 have played an important part in the production of conditions 

 suitable for the formation of glauberite; and that if this could be 

 established, then the occurrence of glendonite, pseudomorphic after 

 glauberite, might be taken as an indication of glacial conditions. 

 This suggestion, taken with the fact that the glendonites always 

 occur in a calcareous mudstone, opens up an interesting field of 

 research in the artificial preparation of glauberite, (which, as far 

 as could be ascertained, has not yet been prepared artificially in the 

 wet way), by attempting to grow the crystals in calcareous mud, 

 under temperature-conditions approximating to those which would 

 be prevalent in waters subject to chilling by glaciers. 



I wish to express my thanks to Dr. C. Anderson, of the Aus- 

 tralian Museum, for the advice he most willingly gave me in con- 

 nection with the crystallographic part of this note; and to Pro- 

 fessor Woolnough for kindly volunteering part of the information 

 contained in the paper, and for suggestions made in discussing the 

 subject with me. 



