xlvi. ABSTRACT OP PROCEEDINGS. 



they will be of a low order, and should a definitive discussion of 

 the orbit be undertaken, then the results deduced will not require 

 material alteration. rL 



4. "On the composition of N. S. Wales Labradorite and Topazes, 



with a comparison of methods for the estimation of Fluorine," 

 by G. Harker, b. Sc. ( Communicated by Professor A. 



LlVERSIDGE, M.A., LL D., F.R.S.) 



The paper gives the composition and properties of a typical 

 labradorite from New England, N. S. Wales, and also the com- 

 position including the water of constitution of two varieties of 

 topazes found in N. S. Wales, one from the Mudgee the other 

 from the New England district. The composition of the first is 

 silica 31-87, alumina 56 "71, fluorine 17*30, water on ignition *25, 

 water of constitution -75; and of the second, silica 31*83, 

 alumina 55*53, fluorine 16*11, water on ignition *38, water of 

 constitution 1*07, the mean of two analyses in each case. It 

 describes also the results obtained for the percentage of fluorine 

 in topaz by three different methods, viz., by fusing the topaz with 

 alkaline carbonates alone (Wohler), by liberating the fluorine as 

 silicon tetra-fluoride and weighing as potassium silicon-fluoride 

 (Liversidge), and by decomposing with alkaline carbonates and 

 silica (Berzelius-Rose). The last method gave the best results, 

 and very probably the whole of the fluorine is obtained by this 

 method. 



5. "Note on a remarkable increase of temperature after dark at 



Seven Oaks, Macleay River," by Hugh Charles Kiddle, 



P. E. Met. Soc. 



During a moderate heat wave on 25, 26, and 27 November, the 

 maximum thermometer recorded 90° to 91*8° at about 10 a.m.; 

 then a sea breeze came in, and by midday the temperature fell to 

 what it had been at 7*30 a.m., and continued to fall under the 

 same influence till at 7 p.m. it stood at 75°. On the 27th shortly 

 after 7 p.m., a thunderstorm which had been working up from 

 the west for half an hour, reached us, but instead of the usually 

 cool brepz s which a thunderstorm brings, we experienced a blast 



