for the year 1868. 11 



of magnesia, and even sulphate of ammonium with it, and 

 in every case the filtrate passed out as drinkable water, with 

 barely traces of the substance previously in solution. Pass- 

 ing hot water in a reverse way through the filter removed 

 the suspended salts and restored the activity of the filtering- 

 medium, which, after continued use, was diminished. 



Some experiments were since tried on the filtration of sea - 

 water, by Mr. Dahlke, and I belie ve he is now engaged in 

 the construction of a large filter for rendering brackish water 

 fit for sheep and cattle at some station on the Darling river* 

 There is no doubt that the kind of filter exhibited is exceed- 

 ingly successful as an ordinary domestic filter, but whether 

 it will become practically successful in so remarkable a use 

 as that of removing salt from sea or very brackish waters, is 

 not yet demonstrated. 



I congratulate you upon these results of your past session, 

 and I regard them as an evidence of increasing activity and 

 an earnest of advancement in the objects of this Society. 



You will be glad to learn that our intercourse with kin- 

 dred societies has increased ; there are now eighty-six 

 learned bodies with which we are in communication and 

 interchange of publications ; forty-one of these are British, 

 thirty-six Continental European, five American, two Asiatic, 

 and Hyq Colonial. Our library has been considerably in- 

 creased by donations from these societies, and a complete 

 catalogue, compiled by your honorary librarian, Dr. Neild, 

 is appended to the second part of the last volume of our 

 Transactions. 



I would now revert to the year's history and present state 

 of our public scientific departments, and in doing so if I 

 speak at more length of matters concerning our Observatory 

 than of the other institutions, it is only because I am better 

 acquainted with the details of its progress. 



In my last address I told you that the Great Southern 



