56 
to the vapour of these substances. For this purpose bis- 
muth and palladium at a moderate heat, and gold at a high 
temperature, afforded distinguishing tests. To determine 
the relative attraction of fluorine for those metals upon 
which it does not act except at high temperatures, they used 
as positive poles of a battery of sixty pair of plates, mois- 
tened fluoride of lead, palladium, platinum, gold, and rho- 
dium. The palladium and platinum were always acted 
upon, the gold occasionally, and the rhodium never; from 
which they suppose that fluorine might be obtained in an 
insulated state, by electrolyzing fluoride of lead in a tube of 
fluor spar, using rhodium as the positive pole. 
They were unable to repeat M. Baudrimont’s experi- 
ments in glass or fluor spar vessels, Supposing that the gas 
he obtained was an oxide of fluorine, they heated in a dry 
glass tube iodic acid and fluoride of mercury; supposing 
that since iodine decomposes fluoride of mercury, the oxygen 
and fluorine, being set free from their combinations with op- 
positely electrical bodies (iodine and mercury), would be in 
the most favourable condition for combining. On the appli- 
cation of a moderate heat a pale yellow vapour rose in the 
tube, which did not act on the glass, and bleached litmus. 
Mr. Mallet read a paper “ On an hitherto unobserved 
Structure discovered in certain Trap Rocks in the County of 
Galway.” . 
The town of Galway is built upon a part of an immense 
trap dyke, which extends under the sea and to a consider- 
able distance up Lough Corrib. Large excavations for a 
dock are now making in this rock at Galway, and afford 
a convenient opportunity of examining its structure. It 
separates the limestone on the east (which it tilts up) from 
the sienite of Cunnemara on the west, (which it overlies or 
mingles with.) 
