THE DESERT SANDSTONE. 309 



and under the microscope shows an eolian character, which is like 

 a true aerial sandstone. The grains have been photographed as 

 seen by an inch objective, and have been figured at plate xxii., fig. 

 4. It is seen that they have a perfectly transparent appearance, 

 being rounded almost as much as the sands of the Sahara. For 

 comparison the grains of the ordinary sandstone are figured at 

 plate xxiii., fig. 8. This is a seam of small thickness as appears 

 from the above figures. The red sandstone underneath it is of a 

 somewhat less rounded character. 



From the above sections it appears that the plateaux are only 

 to a certain extent formed of sandstone. It may be asserted from 

 all I have seen of the formation, that the greater portion of this 

 tableland is granite, and that as the magnesian beds are traced 

 northward they thin out or disappear. 



False-bedded Siliceous Sandstones.— But if the general character 

 of the magnesite rocks suggests their origin it is not so easy to 

 deal with the sandstones which underlie them. These need hardly 

 be described. They are brown, reddish, purple-red, and yellow 

 sandstones with thick more or less horizontal layers and false 

 bedding between. To those who are familiar with the Sydney 

 sandstone, no other description will be necessary than to say that 

 they are similar in stratification and the mode of occurrence. 



The great mass of the Desert Sandstone formation is of this 

 character, and in many places there is no appearance whatever of 

 magnesite strata. The only variation that I can trace amongst 

 this sandstone is that some of it has the grains rounded as if by 

 some aerial attrition, while in other portions they are fine and 

 angular, containing small irregular fragments of white quartz and 

 felspar, not more than an inch in diameter, and mostly less than 

 half that size. Sometimes these are crowded together so as to 

 give a conglomerated appearance, or rather that of coarse angular 

 gravel ; but there are wide areas also with nothing but finely 

 grained sandstone varying only in its many colours. 



These sandstones have been a great problem to every geologist 

 who has studied Australian rocks. The Desert Sandstone was 

 very perplexing to Mr. Daintree, just as the Hawkesbury Sandstone 

 was to the eminent Chas. Darwin. It is now nearly eight years 

 since I wrote a paper on a similar matter, and I suggested that 

 these were sands that had been blown about loosely and accumulated 

 in the form of dunes. It will be observed that there is nothing 

 contrary to this idea in what I am now suggesting. The grains 

 from whatever source they came, whether volcanic, granitic or 

 metamorphic, may have been blown about and probably were 

 blown about in the upper strata ere they were consolidated into 

 stone. It may be observed also that these sand ashbeds are not 

 always hardened into a stone. Every intermediate stage may be 



