(34 ♦/. A. Duvn : Ordovician Sedivients. 



mass provided the material for the Ordovician sediment. These 

 in many cases had to be transported over long distances, so that 

 felspars would be rarely preserved — only those derived from, 

 close at hand would remain as clear grains. 



This work was undertaken at the suggestion of Professor E. 

 W. Skeats, in order to attempt an examination of the Ordovi- 

 cian sediments as W. G. Langford" had done of the Silurian. 

 In order to bring the two works on to a comparative descriptive 

 basis, the writer has set his work out on as similar lines to those 

 of Langford as space would allow. 



Mineralogically, VV. G. Langford's inference that the Ordo- 

 vician and Silurian would contain somewhat similar constituents^ 

 is borne out, but it may be noted that the occurrence of strain, 

 polarisation in the quartz grains is not by any means common.- 

 as Langford inferred may be the case. It is perhaps possible 

 that the Melbourne Silurian sediments have been derived from 

 an area where the Ordovician has been subjected to even still 

 greater compressive forces than in the Bendigo area. Minera- 

 logically, the only difference between the constituents of the two 

 series appears to be the relative absence of sapphire and unaltered 

 biotite in the Ordovician. 



In conclusion the writer wishes to acknowledge his thanks to- 

 the Bendigo School of Mines' officials for the use of their assay 

 laboratory ; to Dr. F. L. Stillwell for the invaluable use of his. 

 rock sections; and to Professor E. W. Skeats and Dr. H. S.. 

 Summers for their occasional excellent advice. 



7. Op. cit. 



8. Op. cit., page 49. 



