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Note on Ked Eain Dust from Australia. 

 By G. C. Karop, M.E.C.S., F.R.M.S. 



{Read April Idth, 1901.) 



On March 20tli of this year I received for examination from 

 Captain C, J. Gray, F.R.G.S., a small sample of Red Rain Dust, 

 collected by him in Melbourne, Victoria, on Dec. 28th, 1896. 



The material was a cinnamon or brick-dust coloured powder in 

 a very fine state of division. Under the microscope it was seen 

 to consist almost entirely of extremely minute amorphous particles, 

 sparsely intermixed with some larger aggregations of the same, 

 which in xylol balsam and by transmitted light appeared of a 

 dull orange tint. 



On going over the preparations field by field, a few other 

 inorganic inclusions and still fewer organic bodies were to be 

 found — the latter consisting for the most part of diatomaceous 

 fragments, but in one or two cases entire valves ; broken sponge 

 spicules, some very much eroded, and also some curved, hyaline 

 objects, pointed at one end and possessing scattered, secondary 

 blunt spines. The exact nature of these last is to me uncertain ; 

 they may be sponge spicules, but I rather incline to the idea that 

 they are siliceous plant hairs. 



The diatoms were generally too much fragmented for certain 

 identification, a minute Surirella and a species of Fragilaria alone 

 being entire. The central portion of what is clearly a Stauroneis, 

 and bits of Epiihemia valves were, however, distinguishable by 

 their markings. 



The dust itself is pretty certainly a ferruginous clay, and no 

 efiervescence or visible efiect was produced by acids. The few 

 inorganic inclusions are minute greenish grains of (?) chlorite or 

 (?) glauconite ; but these, of course, may be quite adventitious. 



In the absence of any knowledge of the geological features of 

 the Melbourne district it is obviously impossible for me to say 

 whether the material examined is of local origin or not. In 



