338 
** As the action of the gas upon glass could not be deter- 
mined, owing to the presence ofthe vapour of hydrofluoric acid, 
I fusedin a bent tube of German glass (such as is used inorganic 
analysis) fluoride of lead. The wire holding the charcoal was 
made to pass through a cork inserted in one end of the tube, 
the other platinum wire merely dipped into the fused fluoride. 
On connecting the wires with the battery, strong electrolytic 
action commenced, bubbles of gas were evolved rapidly at 
the surface of the charcoal, which, on arriving at the surface 
of the fused fluoride of lead, acted instantly upon the glass. 
The litmus paper was not bleached, nor the gold leaf or 
platinum wire acted upon. Whether fluorine would act 
upon perfectly dry cold glass remains to be proved. 
“‘ Conclusion.—F luorine then, when obtained in an insulated 
state, is a colourless gas, possessing properties analogous in 
all respects to those of chlorine; having, like it, strong at- 
tractive powers for hydrogen and metals, but inferior to it 
in negative electrical energy.” 
2, Note on a Compound of Fluorine with Selenium. 
‘** When the vapour of selenium is passed over fluoride of 
fead fused in the platinum apparatus employed in obtaining 
the fluorides of carbon and cyanogen, a seleniuret of lead is 
formed, and crystals similar in form to those of fluoride of 
carbon are condensed in the cold receiver. These crystals 
are soluble in strong hydrofluoric acid. They sublime un- 
altered at a high temperature. They are instantly decom- 
posed by water or acids, in which property they resemble the 
fluorides of sulphur and phosphorus.” 
The President read a paper, by the Rev. Dr. Robinson, 
M.R.1.A., &c., on the recent Employment of Rockets to 
determine the Difference of Longitudes of Armagh and 
Dublin, and on the proposed Extension of this Operation to 
other British Observatories. 
In this paper, after alluding to the recommendation of the 
