METEORIC DUSTS, N.S.W. 245 



resemble, and may be identical with Diatoma vulgare 

 and Surlrella constricta, a few siliceous spicules, some- 

 thing like sponge spicules are also present ; these together 

 with the diatoms are rather more readily detected after 

 treating the dust with nitric acid. A few vegetable fibres, 

 including some filaments of cotton, together with vege- 

 table spores are also revealed by the microscope. There 

 are also a few scattered minute black non-magnetic particles 

 which are probably chrome iron, but the quantity is insuf- 

 ficient for me to satisfy myself on this point. 



A qualitative examination yielded me the following 

 results : — the presence of organic matter, water both 

 hygroscopic and combined, silica both as free quartz and 

 in combination with bases, mainly with alumina in the 

 form of clay; iron, metallic and in combination as oxide, 

 cobalt, and probably nickel, a trace of copper, manganese, 

 lime, magnesia, potash, soda and small quantities of hydro- 

 chloric, sulphuric, phosphoric and carbonic acids. The dust 

 appears to consist mainly of finely divided clay mixed with 

 other substances. 



The hydrochloric acid, as soluble chlorides, is present in 

 rather greater quantity than either the sulphuric or car- 

 bonic acids ; there is but a trace of phosphoric acid. 



An examination with the spectroscope failed to reveal 

 the presence of any rare or unusual element in either the 

 soluble or insoluble portion. 



A quantitative examination gave the following results: 



Moisture at 100° 5*400 



Loss on ignition 9*700 



Silica 58*020 



Alumina 17*184 



Ferrous oxide 1*214 



Ferric oxide 4*237 



Lime 2'270 



Soda traces 



Potash trace 



Undetermined 1*975 



100,000 



