6 TRANSACTIONS OF THE foer i, 
tion of tetrafluoride took place. The clear, yellow liquid gave 
off dense fumes, smelling of fluorine, in large quantity. The 
solution was heated for several days in a covered crucible on 
the water bath, then allowed to stand in a dessicator and heated 
again, and this alternative process was repeated during several 
weeks. The solution was found to give off a smell of hydro- 
fluoric acid and an orange-yellow crystalline substance was 
separated slowly, but only after standing for about two months 
the solution became colourless and free from any dissolved 
tetrafluoride. After this time the solid orange-coloured sub- 
stance was washed with sulphuric acid by decantation. The 
acid was then poured off as completely as possible and the sub- 
stance was decomposed with water, when it yielded lead dioxide 
and a solution containing sulphuric acid but only a small quan- 
tity of hydrofluoric acid. The substance can be therefore only 
lead disulphate Pb (SO,),, analogous to Sn (SO,), and the 
formation requiring a very long time, must have taken place 
according to the following equation : 
PbF,+nH,8SO,—Pb(SO,),+4 HF+(n-2)H,S80,. 
The more the quadrivalent lead is studied, the greater 
becomes its analogy with quadrivalent tin and of course the 
existence of the substances described in the present paper gives 
additional confirmation to the position which lead occupies in 
Mendelejeff’s periodic system. Thirty years ago hardly anyone 
could have predicted that lead would form compounds analo- 
gous not only with those of tin, but also with those of silicon, 
titanium, ziconium, cerium and thorium. 
May, 1894. 
Prof. Hubbard exhibited some gnawed beaver sticks from the 
pond described by him last year (Trans., Vol. XIII., 115,177) 
and commented upon them. 
va 
Reports of summer work were then presented by the follow- 
ing members: Osborn, Britton, Martin, Hallock, van Ingen, 
Kemp, Cox, Pupin and Rees, after which the Academy 
adjourned. 
J. F. Kemp, 
Recording Secretary. 
