THE DESERT SANDSTONE. 315 



lines twisted and undulating like the grain of woody fibre ; and 

 finally a glass structure- like Pele's-hair.* 



Without entering further into the detail of the appearances 

 presented by the sand grains when they are either granitic, 

 metamorphic or volcanic, 1 may sum up by saying that it is. 

 perfectly possible to distinguish between them when they are 

 recent, nor is the evidence entirely lost until completely changed 

 by metamorphic action. 



After having examined a considerable number of specimens of 

 the Desert Sandstone taken from different places, I incline to the 

 conclusion that they are all volcanic sands ; that is to say, speaking 

 now of microscopic appearances only. The reasons for coming to 

 this conclusion are generally the numerous inclusions of foreign 

 matter in the quartz, their nature, and finally the peculiar 

 character of the cavities. I do not pretend that the evidence is. 

 perfectly convincing, and I admit that the inclusions and the 

 minerals are scanty in comparison with what I have been able to 

 gather on recent crater walls. However, it would be difficult to 

 reconcile the appearances in the grains of the Desert Sandstone 

 with any other than a volcanic genesis. Moreover when we add the 

 evidence afforded by the magnesite beds, the peculiar aggregation 

 of these sands, and finally their unfossilliferous character, the 

 conclusions as to their igneous origin become strengthened. 



The weight of evidence becomes however^ very great indeed 

 when we notice, what I have already called attention to, that 

 throughout Australia these sands and sandstones are always found 

 associated with recent volcanic rocks. 



It may appear somewhat unnecessary to bring so many proofs 

 forward on a matter so obvious ; but the lithological character of 

 these sandstones has caused them to be erroneously identified with 

 Mesozoic strata, and even Carboniferous and Devonian. The 

 government geologists will no doubt rectify some of these errors ;, 

 but in the mean time Mr. Clarke's map, founded alone on specimens 

 forwarded to that gentleman, retains them. That lamented 

 geologist gave what he considered to be the best inference in the 

 time at his disposal. I could not record any difference of opinion 

 between myself and this painstaking observer, who was justly 

 considered as the father of Australian geology, without recording 

 my sense of the difficulties under which he laboured and the 

 immense credit due for the work he effected. Mistakes in the 

 early history of any science are what must be expected : steps, 

 have been retraced and new systems adopted over and over again 



* A filamentary variety of obsidian produced by the action of the 

 wind upon the viscid lava projected into the air by the escape of steam 

 from the surface of the lava lake in the crater of Kilauea, Hawaii. Pele 

 is the name of a goddess supposed to inhabit this crater. 



